diff --git a/.php-cs-fixer.php b/.php-cs-fixer.php
index 4958fe4..b9f1624 100644
--- a/.php-cs-fixer.php
+++ b/.php-cs-fixer.php
@@ -37,6 +37,11 @@
         'spacing' => 'one',
     ],
     'self_accessor' => true,
+    'nullable_type_declaration' => ['syntax' => 'union'],
+    'ordered_types' => [
+        'null_adjustment' => 'always_last',
+        'sort_algorithm' => 'none',
+    ],
 ])
     ->setRiskyAllowed(true)
     ->setFinder($finder);
diff --git a/composer.json b/composer.json
index f77ebe9..fbf4ce0 100644
--- a/composer.json
+++ b/composer.json
@@ -29,7 +29,7 @@
     "symfony/serializer": "^5.4 || ^6.3 || ^7.0"
   },
   "require-dev": {
-    "friendsofphp/php-cs-fixer": "3.48",
+    "friendsofphp/php-cs-fixer": "^3.49",
     "guzzlehttp/psr7": "^2.6",
     "monolog/monolog": "^3.5",
     "php-http/curl-client": "^2.3",
diff --git a/src/Client.php b/src/Client.php
index b5f72ba..64cb3a7 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -81,12 +81,12 @@ class Client
 
     public function __construct(
         #[\SensitiveParameter] private readonly string $apiKey,
-        Options $options = null,
-        HttpAsyncClient $httpClient = null,
-        LoggerInterface $logger = null,
-        RequestFactoryInterface $requestFactory = null,
-        StreamFactoryInterface $streamFactory = null,
-        UriFactoryInterface $uriFactory = null,
+        Options|null $options = null,
+        HttpAsyncClient|null $httpClient = null,
+        LoggerInterface|null $logger = null,
+        RequestFactoryInterface|null $requestFactory = null,
+        StreamFactoryInterface|null $streamFactory = null,
+        UriFactoryInterface|null $uriFactory = null,
     ) {
         $this->options = $options ?: new Options();
         $this->logger = $logger ?: new NullLogger();
@@ -159,7 +159,7 @@ public function deleteRaw(string|UriInterface $uri): ResponseInterface
         return $this->requestRaw('DELETE', $uri);
     }
 
-    private function requestRaw(string $method, string|UriInterface $uri, array|\JsonSerializable $payload = null): ResponseInterface
+    private function requestRaw(string $method, string|UriInterface $uri, array|\JsonSerializable|null $payload = null): ResponseInterface
     {
         if (\is_string($uri)) {
             $components = \parse_url($this->options->environment->baseUrl());
diff --git a/src/Entities/Collections/AddressCollection.php b/src/Entities/Collections/AddressCollection.php
index 0f98a9c..0f02d3c 100644
--- a/src/Entities/Collections/AddressCollection.php
+++ b/src/Entities/Collections/AddressCollection.php
@@ -15,7 +15,7 @@
 
 class AddressCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Address => Address::from($item), $itemsData),
diff --git a/src/Entities/Collections/AdjustmentCollection.php b/src/Entities/Collections/AdjustmentCollection.php
index e18d618..62e14cb 100644
--- a/src/Entities/Collections/AdjustmentCollection.php
+++ b/src/Entities/Collections/AdjustmentCollection.php
@@ -15,7 +15,7 @@
 
 class AdjustmentCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Adjustment => Adjustment::from($item), $itemsData),
diff --git a/src/Entities/Collections/BusinessCollection.php b/src/Entities/Collections/BusinessCollection.php
index 749dceb..ef2663f 100644
--- a/src/Entities/Collections/BusinessCollection.php
+++ b/src/Entities/Collections/BusinessCollection.php
@@ -15,7 +15,7 @@
 
 class BusinessCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Business => Business::from($item), $itemsData),
diff --git a/src/Entities/Collections/Collection.php b/src/Entities/Collections/Collection.php
index a816460..728ef4c 100644
--- a/src/Entities/Collections/Collection.php
+++ b/src/Entities/Collections/Collection.php
@@ -12,11 +12,11 @@ abstract class Collection implements \Iterator
 
     public function __construct(
         protected array $items,
-        protected ?Paginator $paginator = null,
+        protected Paginator|null $paginator = null,
     ) {
     }
 
-    abstract public static function from(array $data, ?Paginator $paginator): self;
+    abstract public static function from(array $data, Paginator|null $paginator): self;
 
     public function current(): Entity
     {
diff --git a/src/Entities/Collections/CreditBalanceCollection.php b/src/Entities/Collections/CreditBalanceCollection.php
index c9f3087..05f11cd 100644
--- a/src/Entities/Collections/CreditBalanceCollection.php
+++ b/src/Entities/Collections/CreditBalanceCollection.php
@@ -15,7 +15,7 @@
 
 class CreditBalanceCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): CreditBalance => CreditBalance::from($item), $itemsData),
diff --git a/src/Entities/Collections/CustomerCollection.php b/src/Entities/Collections/CustomerCollection.php
index c909e87..1d3f303 100644
--- a/src/Entities/Collections/CustomerCollection.php
+++ b/src/Entities/Collections/CustomerCollection.php
@@ -15,7 +15,7 @@
 
 class CustomerCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Customer => Customer::from($item), $itemsData),
diff --git a/src/Entities/Collections/DiscountCollection.php b/src/Entities/Collections/DiscountCollection.php
index 2a1b718..aa188d3 100644
--- a/src/Entities/Collections/DiscountCollection.php
+++ b/src/Entities/Collections/DiscountCollection.php
@@ -15,7 +15,7 @@
 
 class DiscountCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Discount => Discount::from($item), $itemsData),
diff --git a/src/Entities/Collections/EventCollection.php b/src/Entities/Collections/EventCollection.php
index 588c5b2..b3b1e5e 100644
--- a/src/Entities/Collections/EventCollection.php
+++ b/src/Entities/Collections/EventCollection.php
@@ -15,7 +15,7 @@
 
 class EventCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Event => Event::from($item), $itemsData),
diff --git a/src/Entities/Collections/EventTypeCollection.php b/src/Entities/Collections/EventTypeCollection.php
index c3d54ef..2b736be 100644
--- a/src/Entities/Collections/EventTypeCollection.php
+++ b/src/Entities/Collections/EventTypeCollection.php
@@ -15,7 +15,7 @@
 
 class EventTypeCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): EventType => EventType::from($item), $itemsData),
diff --git a/src/Entities/Collections/NotificationCollection.php b/src/Entities/Collections/NotificationCollection.php
index 1aa8d99..fa053b6 100644
--- a/src/Entities/Collections/NotificationCollection.php
+++ b/src/Entities/Collections/NotificationCollection.php
@@ -15,7 +15,7 @@
 
 class NotificationCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Notification => Notification::from($item), $itemsData),
diff --git a/src/Entities/Collections/NotificationLogCollection.php b/src/Entities/Collections/NotificationLogCollection.php
index 271c1c5..035f2c4 100644
--- a/src/Entities/Collections/NotificationLogCollection.php
+++ b/src/Entities/Collections/NotificationLogCollection.php
@@ -15,7 +15,7 @@
 
 class NotificationLogCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): NotificationLog => NotificationLog::from($item), $itemsData),
diff --git a/src/Entities/Collections/NotificationSettingCollection.php b/src/Entities/Collections/NotificationSettingCollection.php
index 1e3067c..eaa098f 100644
--- a/src/Entities/Collections/NotificationSettingCollection.php
+++ b/src/Entities/Collections/NotificationSettingCollection.php
@@ -15,7 +15,7 @@
 
 class NotificationSettingCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): NotificationSetting => NotificationSetting::from($item), $itemsData),
diff --git a/src/Entities/Collections/PriceCollection.php b/src/Entities/Collections/PriceCollection.php
index 32fc87f..7fb0f5a 100644
--- a/src/Entities/Collections/PriceCollection.php
+++ b/src/Entities/Collections/PriceCollection.php
@@ -15,7 +15,7 @@
 
 class PriceCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Price => Price::from($item), $itemsData),
diff --git a/src/Entities/Collections/ProductCollection.php b/src/Entities/Collections/ProductCollection.php
index 3a23250..0c4479c 100644
--- a/src/Entities/Collections/ProductCollection.php
+++ b/src/Entities/Collections/ProductCollection.php
@@ -15,7 +15,7 @@
 
 class ProductCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Product => Product::from($item), $itemsData),
diff --git a/src/Entities/Collections/ReportCollection.php b/src/Entities/Collections/ReportCollection.php
index d5fa608..3cdb771 100644
--- a/src/Entities/Collections/ReportCollection.php
+++ b/src/Entities/Collections/ReportCollection.php
@@ -15,7 +15,7 @@
 
 class ReportCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Report => Report::from($item), $itemsData),
diff --git a/src/Entities/Collections/SubscriptionCollection.php b/src/Entities/Collections/SubscriptionCollection.php
index 40fdc8c..622179d 100644
--- a/src/Entities/Collections/SubscriptionCollection.php
+++ b/src/Entities/Collections/SubscriptionCollection.php
@@ -15,7 +15,7 @@
 
 class SubscriptionCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Subscription => Subscription::from($item), $itemsData),
diff --git a/src/Entities/Collections/SubscriptionPreviewCollection.php b/src/Entities/Collections/SubscriptionPreviewCollection.php
index 2258580..f9bd1fb 100644
--- a/src/Entities/Collections/SubscriptionPreviewCollection.php
+++ b/src/Entities/Collections/SubscriptionPreviewCollection.php
@@ -15,7 +15,7 @@
 
 class SubscriptionPreviewCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): SubscriptionPreview => SubscriptionPreview::from($item), $itemsData),
diff --git a/src/Entities/Collections/SubscriptionsTransactionCollection.php b/src/Entities/Collections/SubscriptionsTransactionCollection.php
index 0a18087..63d8c8a 100644
--- a/src/Entities/Collections/SubscriptionsTransactionCollection.php
+++ b/src/Entities/Collections/SubscriptionsTransactionCollection.php
@@ -15,7 +15,7 @@
 
 class SubscriptionsTransactionCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): SubscriptionTransaction => SubscriptionTransaction::from($item), $itemsData),
diff --git a/src/Entities/Collections/TransactionCollection.php b/src/Entities/Collections/TransactionCollection.php
index 7f1356d..5cec347 100644
--- a/src/Entities/Collections/TransactionCollection.php
+++ b/src/Entities/Collections/TransactionCollection.php
@@ -15,7 +15,7 @@
 
 class TransactionCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): Transaction => Transaction::from($item), $itemsData),
diff --git a/src/Entities/Collections/TransactionPreviewCollection.php b/src/Entities/Collections/TransactionPreviewCollection.php
index 1e18466..37310f3 100644
--- a/src/Entities/Collections/TransactionPreviewCollection.php
+++ b/src/Entities/Collections/TransactionPreviewCollection.php
@@ -15,7 +15,7 @@
 
 class TransactionPreviewCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): TransactionPreview => TransactionPreview::from($item), $itemsData),
diff --git a/src/Entities/Collections/TransactionsDataCollection.php b/src/Entities/Collections/TransactionsDataCollection.php
index 02503b5..4258ec2 100644
--- a/src/Entities/Collections/TransactionsDataCollection.php
+++ b/src/Entities/Collections/TransactionsDataCollection.php
@@ -15,7 +15,7 @@
 
 class TransactionsDataCollection extends Collection
 {
-    public static function from(array $itemsData, Paginator $paginator = null): self
+    public static function from(array $itemsData, Paginator|null $paginator = null): self
     {
         return new self(
             array_map(fn (array $item): TransactionData => TransactionData::from($item), $itemsData),
diff --git a/src/Entities/DateTime.php b/src/Entities/DateTime.php
index f80a607..17190b1 100644
--- a/src/Entities/DateTime.php
+++ b/src/Entities/DateTime.php
@@ -14,7 +14,7 @@ public function __construct(string $datetime = 'now')
         parent::__construct(datetime: $datetime, timezone: new \DateTimeZone('UTC'));
     }
 
-    public function format(string $format = null): string
+    public function format(string|null $format = null): string
     {
         return parent::format($format ?? self::PADDLE_RFC3339);
     }
diff --git a/src/Entities/Product.php b/src/Entities/Product.php
index 4126eb8..fd6477d 100644
--- a/src/Entities/Product.php
+++ b/src/Entities/Product.php
@@ -26,7 +26,7 @@ public function __construct(
         public string|null $description,
         public CatalogType|null $type,
         public TaxCategory $taxCategory,
-        public null|string $imageUrl,
+        public string|null $imageUrl,
         public CustomData|null $customData,
         public Status $status,
         public \DateTimeInterface|null $createdAt,
diff --git a/src/Entities/Subscription/SubscriptionNonCatalogProduct.php b/src/Entities/Subscription/SubscriptionNonCatalogProduct.php
index 72b2c18..83d21f1 100644
--- a/src/Entities/Subscription/SubscriptionNonCatalogProduct.php
+++ b/src/Entities/Subscription/SubscriptionNonCatalogProduct.php
@@ -22,7 +22,7 @@ public function __construct(
         public string|null $description,
         public CatalogType|null $type,
         public TaxCategory $taxCategory,
-        public null|string $imageUrl,
+        public string|null $imageUrl,
         public CustomData|null $customData,
     ) {
     }
diff --git a/src/Entities/Transaction/TransactionNonCatalogProduct.php b/src/Entities/Transaction/TransactionNonCatalogProduct.php
index 7a48476..533eb30 100644
--- a/src/Entities/Transaction/TransactionNonCatalogProduct.php
+++ b/src/Entities/Transaction/TransactionNonCatalogProduct.php
@@ -20,7 +20,7 @@ public function __construct(
         public string $name,
         public string|null $description,
         public TaxCategory $taxCategory,
-        public null|string $imageUrl,
+        public string|null $imageUrl,
         public CustomData|null $customData,
     ) {
     }
diff --git a/src/Notifications/Verifier.php b/src/Notifications/Verifier.php
index ea12c70..b7008e2 100644
--- a/src/Notifications/Verifier.php
+++ b/src/Notifications/Verifier.php
@@ -9,7 +9,7 @@
 final class Verifier
 {
     public function __construct(
-        private readonly ?int $maximumVariance = 5,
+        private readonly int|null $maximumVariance = 5,
     ) {
     }
 
diff --git a/src/Resources/Addresses/Operations/CreateAddress.php b/src/Resources/Addresses/Operations/CreateAddress.php
index c795387..5e5700d 100644
--- a/src/Resources/Addresses/Operations/CreateAddress.php
+++ b/src/Resources/Addresses/Operations/CreateAddress.php
@@ -15,13 +15,13 @@ class CreateAddress implements \JsonSerializable
 
     public function __construct(
         public readonly CountryCode $countryCode,
-        public readonly string|null|Undefined $description = new Undefined(),
-        public readonly string|null|Undefined $firstLine = new Undefined(),
-        public readonly string|null|Undefined $secondLine = new Undefined(),
-        public readonly string|null|Undefined $city = new Undefined(),
-        public readonly string|null|Undefined $postalCode = new Undefined(),
-        public readonly string|null|Undefined $region = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly string|Undefined|null $description = new Undefined(),
+        public readonly string|Undefined|null $firstLine = new Undefined(),
+        public readonly string|Undefined|null $secondLine = new Undefined(),
+        public readonly string|Undefined|null $city = new Undefined(),
+        public readonly string|Undefined|null $postalCode = new Undefined(),
+        public readonly string|Undefined|null $region = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
     ) {
     }
 
diff --git a/src/Resources/Addresses/Operations/ListAddresses.php b/src/Resources/Addresses/Operations/ListAddresses.php
index bbae867..d13e766 100644
--- a/src/Resources/Addresses/Operations/ListAddresses.php
+++ b/src/Resources/Addresses/Operations/ListAddresses.php
@@ -12,10 +12,10 @@
 class ListAddresses implements HasParameters
 {
     public function __construct(
-        private readonly ?Pager $pager = null,
+        private readonly Pager|null $pager = null,
         private readonly array $ids = [],
         private readonly array $statuses = [],
-        private readonly ?string $search = null,
+        private readonly string|null $search = null,
     ) {
         if ($invalid = array_filter($this->ids, fn ($value): bool => ! is_string($value))) {
             throw InvalidArgumentException::arrayContainsInvalidTypes('ids', 'string', implode(', ', $invalid));
diff --git a/src/Resources/Addresses/Operations/UpdateAddress.php b/src/Resources/Addresses/Operations/UpdateAddress.php
index 2b1312b..27c935b 100644
--- a/src/Resources/Addresses/Operations/UpdateAddress.php
+++ b/src/Resources/Addresses/Operations/UpdateAddress.php
@@ -16,13 +16,13 @@ class UpdateAddress implements \JsonSerializable
 
     public function __construct(
         public readonly CountryCode|Undefined $countryCode = new Undefined(),
-        public readonly string|null|Undefined $description = new Undefined(),
-        public readonly string|null|Undefined $firstLine = new Undefined(),
-        public readonly string|null|Undefined $secondLine = new Undefined(),
-        public readonly string|null|Undefined $city = new Undefined(),
-        public readonly string|null|Undefined $postalCode = new Undefined(),
-        public readonly string|null|Undefined $region = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly string|Undefined|null $description = new Undefined(),
+        public readonly string|Undefined|null $firstLine = new Undefined(),
+        public readonly string|Undefined|null $secondLine = new Undefined(),
+        public readonly string|Undefined|null $city = new Undefined(),
+        public readonly string|Undefined|null $postalCode = new Undefined(),
+        public readonly string|Undefined|null $region = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
         public readonly Status|Undefined $status = new Undefined(),
     ) {
     }
diff --git a/src/Resources/Adjustments/Operations/ListAdjustments.php b/src/Resources/Adjustments/Operations/ListAdjustments.php
index 6914503..8574092 100644
--- a/src/Resources/Adjustments/Operations/ListAdjustments.php
+++ b/src/Resources/Adjustments/Operations/ListAdjustments.php
@@ -22,13 +22,13 @@ class ListAdjustments implements HasParameters
      * @throws InvalidArgumentException On invalid array arguments
      */
     public function __construct(
-        private readonly ?Pager $pager = null,
+        private readonly Pager|null $pager = null,
         private readonly array $ids = [],
         private readonly array $statuses = [],
         private readonly array $customerIds = [],
         private readonly array $transactionIds = [],
         private readonly array $subscriptionIds = [],
-        private readonly ?Action $action = null,
+        private readonly Action|null $action = null,
     ) {
         if ($invalid = array_filter($this->ids, fn ($value): bool => ! is_string($value))) {
             throw InvalidArgumentException::arrayContainsInvalidTypes('ids', 'string', implode(', ', $invalid));
diff --git a/src/Resources/Businesses/Operations/CreateBusiness.php b/src/Resources/Businesses/Operations/CreateBusiness.php
index 0320715..9e6bd27 100644
--- a/src/Resources/Businesses/Operations/CreateBusiness.php
+++ b/src/Resources/Businesses/Operations/CreateBusiness.php
@@ -18,10 +18,10 @@ class CreateBusiness implements \JsonSerializable
      */
     public function __construct(
         public readonly string $name,
-        public readonly string|null|Undefined $companyNumber = new Undefined(),
-        public readonly string|null|Undefined $taxIdentifier = new Undefined(),
+        public readonly string|Undefined|null $companyNumber = new Undefined(),
+        public readonly string|Undefined|null $taxIdentifier = new Undefined(),
         public readonly array|Undefined $contacts = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
     ) {
     }
 
diff --git a/src/Resources/Businesses/Operations/ListBusinesses.php b/src/Resources/Businesses/Operations/ListBusinesses.php
index 6aade5f..38d80d1 100644
--- a/src/Resources/Businesses/Operations/ListBusinesses.php
+++ b/src/Resources/Businesses/Operations/ListBusinesses.php
@@ -18,10 +18,10 @@ class ListBusinesses implements HasParameters
      * @throws InvalidArgumentException On invalid array contents
      */
     public function __construct(
-        private readonly ?Pager $pager = null,
+        private readonly Pager|null $pager = null,
         private readonly array $ids = [],
         private readonly array $statuses = [],
-        private readonly ?string $search = null,
+        private readonly string|null $search = null,
     ) {
         if ($invalid = array_filter($this->ids, fn ($value): bool => ! is_string($value))) {
             throw InvalidArgumentException::arrayContainsInvalidTypes('ids', 'string', implode(', ', $invalid));
diff --git a/src/Resources/Businesses/Operations/UpdateBusiness.php b/src/Resources/Businesses/Operations/UpdateBusiness.php
index 2fe3ccd..80d9824 100644
--- a/src/Resources/Businesses/Operations/UpdateBusiness.php
+++ b/src/Resources/Businesses/Operations/UpdateBusiness.php
@@ -19,10 +19,10 @@ class UpdateBusiness implements \JsonSerializable
      */
     public function __construct(
         public readonly string|Undefined $name = new Undefined(),
-        public readonly string|null|Undefined $companyNumber = new Undefined(),
-        public readonly string|null|Undefined $taxIdentifier = new Undefined(),
+        public readonly string|Undefined|null $companyNumber = new Undefined(),
+        public readonly string|Undefined|null $taxIdentifier = new Undefined(),
         public readonly array|Undefined $contacts = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
         public readonly Status|Undefined $status = new Undefined(),
     ) {
     }
diff --git a/src/Resources/Customers/Operations/CreateCustomer.php b/src/Resources/Customers/Operations/CreateCustomer.php
index 9d6de44..23274ef 100644
--- a/src/Resources/Customers/Operations/CreateCustomer.php
+++ b/src/Resources/Customers/Operations/CreateCustomer.php
@@ -14,8 +14,8 @@ class CreateCustomer implements \JsonSerializable
 
     public function __construct(
         public readonly string $email,
-        public readonly string|null|Undefined $name = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly string|Undefined|null $name = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
         public readonly string|Undefined $locale = new Undefined(),
     ) {
     }
diff --git a/src/Resources/Customers/Operations/ListCustomers.php b/src/Resources/Customers/Operations/ListCustomers.php
index a594498..cf378d1 100644
--- a/src/Resources/Customers/Operations/ListCustomers.php
+++ b/src/Resources/Customers/Operations/ListCustomers.php
@@ -18,10 +18,10 @@ class ListCustomers implements HasParameters
      * @throws InvalidArgumentException On invalid array contents
      */
     public function __construct(
-        private readonly ?Pager $pager = null,
+        private readonly Pager|null $pager = null,
         private readonly array $ids = [],
         private readonly array $statuses = [],
-        private readonly ?string $search = null,
+        private readonly string|null $search = null,
         private readonly array $emails = [],
     ) {
         if ($invalid = array_filter($this->ids, fn ($value): bool => ! is_string($value))) {
diff --git a/src/Resources/Customers/Operations/UpdateCustomer.php b/src/Resources/Customers/Operations/UpdateCustomer.php
index db85137..15626aa 100644
--- a/src/Resources/Customers/Operations/UpdateCustomer.php
+++ b/src/Resources/Customers/Operations/UpdateCustomer.php
@@ -15,8 +15,8 @@ class UpdateCustomer implements \JsonSerializable
 
     public function __construct(
         public readonly string|Undefined $email = new Undefined(),
-        public readonly string|null|Undefined $name = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly string|Undefined|null $name = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
         public readonly string|Undefined $locale = new Undefined(),
         public readonly Status|Undefined $status = new Undefined(),
     ) {
diff --git a/src/Resources/Discounts/Operations/CreateDiscount.php b/src/Resources/Discounts/Operations/CreateDiscount.php
index 5028324..8c9b611 100644
--- a/src/Resources/Discounts/Operations/CreateDiscount.php
+++ b/src/Resources/Discounts/Operations/CreateDiscount.php
@@ -23,11 +23,11 @@ public function __construct(
         public readonly bool $enabledForCheckout,
         public readonly bool $recur,
         public readonly CurrencyCode $currencyCode,
-        public readonly string|null|Undefined $code = new Undefined(),
-        public readonly int|null|Undefined $maximumRecurringIntervals = new Undefined(),
-        public readonly int|null|Undefined $usageLimit = new Undefined(),
-        public readonly array|null|Undefined $restrictTo = new Undefined(),
-        public readonly string|null|Undefined $expiresAt = new Undefined(),
+        public readonly string|Undefined|null $code = new Undefined(),
+        public readonly int|Undefined|null $maximumRecurringIntervals = new Undefined(),
+        public readonly int|Undefined|null $usageLimit = new Undefined(),
+        public readonly array|Undefined|null $restrictTo = new Undefined(),
+        public readonly string|Undefined|null $expiresAt = new Undefined(),
     ) {
     }
 
diff --git a/src/Resources/Discounts/Operations/ListDiscounts.php b/src/Resources/Discounts/Operations/ListDiscounts.php
index 5bfcc1c..6ac6422 100644
--- a/src/Resources/Discounts/Operations/ListDiscounts.php
+++ b/src/Resources/Discounts/Operations/ListDiscounts.php
@@ -19,7 +19,7 @@ class ListDiscounts implements HasParameters
      * @throws InvalidArgumentException On invalid array contents
      */
     public function __construct(
-        private readonly ?Pager $pager = null,
+        private readonly Pager|null $pager = null,
         private readonly array $ids = [],
         private readonly array $statuses = [],
         private readonly array $codes = [],
diff --git a/src/Resources/Discounts/Operations/UpdateDiscount.php b/src/Resources/Discounts/Operations/UpdateDiscount.php
index beb03a4..7378394 100644
--- a/src/Resources/Discounts/Operations/UpdateDiscount.php
+++ b/src/Resources/Discounts/Operations/UpdateDiscount.php
@@ -24,11 +24,11 @@ public function __construct(
         public readonly bool|Undefined $enabledForCheckout = new Undefined(),
         public readonly bool|Undefined $recur = new Undefined(),
         public readonly CurrencyCode|Undefined $currencyCode = new Undefined(),
-        public readonly string|null|Undefined $code = new Undefined(),
-        public readonly int|null|Undefined $maximumRecurringIntervals = new Undefined(),
-        public readonly int|null|Undefined $usageLimit = new Undefined(),
-        public readonly array|null|Undefined $restrictTo = new Undefined(),
-        public readonly string|null|Undefined $expiresAt = new Undefined(),
+        public readonly string|Undefined|null $code = new Undefined(),
+        public readonly int|Undefined|null $maximumRecurringIntervals = new Undefined(),
+        public readonly int|Undefined|null $usageLimit = new Undefined(),
+        public readonly array|Undefined|null $restrictTo = new Undefined(),
+        public readonly string|Undefined|null $expiresAt = new Undefined(),
         public readonly DiscountStatus|Undefined $status = new Undefined(),
     ) {
     }
diff --git a/src/Resources/Events/Operations/ListEvents.php b/src/Resources/Events/Operations/ListEvents.php
index 5cb5008..d2615e5 100644
--- a/src/Resources/Events/Operations/ListEvents.php
+++ b/src/Resources/Events/Operations/ListEvents.php
@@ -9,7 +9,7 @@
 
 class ListEvents implements HasParameters
 {
-    public function __construct(private readonly ?Pager $pager = null)
+    public function __construct(private readonly Pager|null $pager = null)
     {
     }
 
diff --git a/src/Resources/NotificationLogs/Operations/ListNotificationLogs.php b/src/Resources/NotificationLogs/Operations/ListNotificationLogs.php
index 9a4b598..e323a8c 100644
--- a/src/Resources/NotificationLogs/Operations/ListNotificationLogs.php
+++ b/src/Resources/NotificationLogs/Operations/ListNotificationLogs.php
@@ -9,7 +9,7 @@
 
 class ListNotificationLogs implements HasParameters
 {
-    public function __construct(private readonly ?Pager $pager = null)
+    public function __construct(private readonly Pager|null $pager = null)
     {
     }
 
diff --git a/src/Resources/Notifications/Operations/ListNotifications.php b/src/Resources/Notifications/Operations/ListNotifications.php
index 871b9c5..e774087 100644
--- a/src/Resources/Notifications/Operations/ListNotifications.php
+++ b/src/Resources/Notifications/Operations/ListNotifications.php
@@ -16,7 +16,7 @@ class ListNotifications implements HasParameters
      * @param array<NotificationStatus> $status
      */
     public function __construct(
-        private readonly ?Pager $pager = null,
+        private readonly Pager|null $pager = null,
         private readonly array $notificationSettingId = [],
         private readonly string|null $search = null,
         private readonly array $status = [],
diff --git a/src/Resources/Prices/Operations/CreatePrice.php b/src/Resources/Prices/Operations/CreatePrice.php
index 1798674..4407a29 100644
--- a/src/Resources/Prices/Operations/CreatePrice.php
+++ b/src/Resources/Prices/Operations/CreatePrice.php
@@ -25,12 +25,12 @@ public function __construct(
         public readonly string $description,
         public readonly string $productId,
         public readonly Money $unitPrice,
-        public readonly string|null|Undefined $name = new Undefined(),
-        public readonly CatalogType|null|Undefined $type = new Undefined(),
+        public readonly string|Undefined|null $name = new Undefined(),
+        public readonly CatalogType|Undefined|null $type = new Undefined(),
         public readonly array|Undefined $unitPriceOverrides = new Undefined(),
         public readonly TaxMode|Undefined $taxMode = new Undefined(),
-        public readonly TimePeriod|null|Undefined $trialPeriod = new Undefined(),
-        public readonly TimePeriod|null|Undefined $billingCycle = new Undefined(),
+        public readonly TimePeriod|Undefined|null $trialPeriod = new Undefined(),
+        public readonly TimePeriod|Undefined|null $billingCycle = new Undefined(),
         public readonly PriceQuantity|Undefined $quantity = new Undefined(),
         public readonly CustomData|Undefined $customData = new Undefined(),
     ) {
diff --git a/src/Resources/Prices/Operations/ListPrices.php b/src/Resources/Prices/Operations/ListPrices.php
index 7452266..73bb715 100644
--- a/src/Resources/Prices/Operations/ListPrices.php
+++ b/src/Resources/Prices/Operations/ListPrices.php
@@ -23,13 +23,13 @@ class ListPrices implements HasParameters
      * @throws InvalidArgumentException If includes, ids, statuses or taxCategories contain the incorrect type
      */
     public function __construct(
-        private readonly ?Pager $pager = null,
+        private readonly Pager|null $pager = null,
         private readonly array $includes = [],
         private readonly array $ids = [],
         private readonly array $types = [],
         private readonly array $productIds = [],
         private readonly array $statuses = [],
-        private readonly ?bool $recurring = null,
+        private readonly bool|null $recurring = null,
     ) {
         if ($invalid = array_filter($this->includes, fn ($value): bool => ! $value instanceof Includes)) {
             throw InvalidArgumentException::arrayContainsInvalidTypes('includes', Includes::class, implode(', ', $invalid));
diff --git a/src/Resources/Prices/Operations/UpdatePrice.php b/src/Resources/Prices/Operations/UpdatePrice.php
index ba64ef9..9bb40ba 100644
--- a/src/Resources/Prices/Operations/UpdatePrice.php
+++ b/src/Resources/Prices/Operations/UpdatePrice.php
@@ -24,16 +24,16 @@ class UpdatePrice implements \JsonSerializable
      */
     public function __construct(
         public readonly string|Undefined $description = new Undefined(),
-        public readonly string|null|Undefined $name = new Undefined(),
+        public readonly string|Undefined|null $name = new Undefined(),
         public readonly CatalogType|Undefined $type = new Undefined(),
-        public readonly TimePeriod|null|Undefined $billingCycle = new Undefined(),
-        public readonly TimePeriod|null|Undefined $trialPeriod = new Undefined(),
+        public readonly TimePeriod|Undefined|null $billingCycle = new Undefined(),
+        public readonly TimePeriod|Undefined|null $trialPeriod = new Undefined(),
         public readonly TaxMode|Undefined $taxMode = new Undefined(),
         public readonly Money|Undefined $unitPrice = new Undefined(),
         public readonly array|Undefined $unitPriceOverrides = new Undefined(),
         public readonly PriceQuantity|Undefined $quantity = new Undefined(),
         public readonly Status|Undefined $status = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
     ) {
     }
 
diff --git a/src/Resources/PricingPreviews/Operations/PreviewPrice.php b/src/Resources/PricingPreviews/Operations/PreviewPrice.php
index 0728e0d..31773cb 100644
--- a/src/Resources/PricingPreviews/Operations/PreviewPrice.php
+++ b/src/Resources/PricingPreviews/Operations/PreviewPrice.php
@@ -19,13 +19,13 @@ class PreviewPrice implements \JsonSerializable
      */
     public function __construct(
         public readonly array $items,
-        public readonly string|null|Undefined $customerId = new Undefined(),
-        public readonly string|null|Undefined $addressId = new Undefined(),
-        public readonly string|null|Undefined $businessId = new Undefined(),
+        public readonly string|Undefined|null $customerId = new Undefined(),
+        public readonly string|Undefined|null $addressId = new Undefined(),
+        public readonly string|Undefined|null $businessId = new Undefined(),
         public readonly CurrencyCode|Undefined $currencyCode = new Undefined(),
-        public readonly string|null|Undefined $discountId = new Undefined(),
-        public readonly AddressPreview|null|Undefined $address = new Undefined(),
-        public readonly string|null|Undefined $customerIpAddress = new Undefined(),
+        public readonly string|Undefined|null $discountId = new Undefined(),
+        public readonly AddressPreview|Undefined|null $address = new Undefined(),
+        public readonly string|Undefined|null $customerIpAddress = new Undefined(),
     ) {
     }
 
diff --git a/src/Resources/Products/Operations/CreateProduct.php b/src/Resources/Products/Operations/CreateProduct.php
index 542c661..e7c037c 100644
--- a/src/Resources/Products/Operations/CreateProduct.php
+++ b/src/Resources/Products/Operations/CreateProduct.php
@@ -17,10 +17,10 @@ class CreateProduct implements \JsonSerializable
     public function __construct(
         public readonly string $name,
         public readonly TaxCategory $taxCategory,
-        public readonly CatalogType|null|Undefined $type = new Undefined(),
-        public readonly string|null|Undefined $description = new Undefined(),
-        public readonly string|null|Undefined $imageUrl = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly CatalogType|Undefined|null $type = new Undefined(),
+        public readonly string|Undefined|null $description = new Undefined(),
+        public readonly string|Undefined|null $imageUrl = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
     ) {
     }
 
diff --git a/src/Resources/Products/Operations/ListProducts.php b/src/Resources/Products/Operations/ListProducts.php
index d682c63..5b4d68c 100644
--- a/src/Resources/Products/Operations/ListProducts.php
+++ b/src/Resources/Products/Operations/ListProducts.php
@@ -24,7 +24,7 @@ class ListProducts implements HasParameters
      * @throws InvalidArgumentException
      */
     public function __construct(
-        private readonly ?Pager $pager = null,
+        private readonly Pager|null $pager = null,
         private readonly array $includes = [],
         private readonly array $ids = [],
         private readonly array $types = [],
diff --git a/src/Resources/Products/Operations/UpdateProduct.php b/src/Resources/Products/Operations/UpdateProduct.php
index 35ce035..82fbf21 100644
--- a/src/Resources/Products/Operations/UpdateProduct.php
+++ b/src/Resources/Products/Operations/UpdateProduct.php
@@ -17,11 +17,11 @@ class UpdateProduct implements \JsonSerializable
 
     public function __construct(
         public readonly string|Undefined $name = new Undefined(),
-        public readonly string|null|Undefined $description = new Undefined(),
-        public readonly CatalogType|null|Undefined $type = new Undefined(),
+        public readonly string|Undefined|null $description = new Undefined(),
+        public readonly CatalogType|Undefined|null $type = new Undefined(),
         public readonly TaxCategory|Undefined $taxCategory = new Undefined(),
-        public readonly string|null|Undefined $imageUrl = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly string|Undefined|null $imageUrl = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
         public readonly Status|Undefined $status = new Undefined(),
     ) {
     }
diff --git a/src/Resources/Reports/Operations/ListReports.php b/src/Resources/Reports/Operations/ListReports.php
index 0fde3de..a0a2cb3 100644
--- a/src/Resources/Reports/Operations/ListReports.php
+++ b/src/Resources/Reports/Operations/ListReports.php
@@ -17,7 +17,7 @@ class ListReports implements HasParameters
      * @throws InvalidArgumentException
      */
     public function __construct(
-        private readonly ?Pager $pager = null,
+        private readonly Pager|null $pager = null,
         private readonly array $statuses = [],
     ) {
         if ($invalid = array_filter($this->statuses, fn ($value): bool => ! $value instanceof ReportStatus)) {
diff --git a/src/Resources/Shared/Operations/List/DateComparison.php b/src/Resources/Shared/Operations/List/DateComparison.php
index d3fec5d..18c47b8 100644
--- a/src/Resources/Shared/Operations/List/DateComparison.php
+++ b/src/Resources/Shared/Operations/List/DateComparison.php
@@ -10,7 +10,7 @@ class DateComparison
 {
     public function __construct(
         public readonly \DateTimeInterface $date,
-        public readonly ?Comparator $comparator = null,
+        public readonly Comparator|null $comparator = null,
     ) {
     }
 
diff --git a/src/Resources/Shared/Operations/List/Pager.php b/src/Resources/Shared/Operations/List/Pager.php
index dc373be..16af566 100644
--- a/src/Resources/Shared/Operations/List/Pager.php
+++ b/src/Resources/Shared/Operations/List/Pager.php
@@ -8,7 +8,7 @@
 
 class Pager implements HasParameters
 {
-    public function __construct(private readonly ?string $after = null, private ?OrderBy $orderBy = null, private readonly int $perPage = 50)
+    public function __construct(private readonly string|null $after = null, private OrderBy|null $orderBy = null, private readonly int $perPage = 50)
     {
         $this->orderBy ??= OrderBy::idAscending();
     }
diff --git a/src/Resources/Subscriptions/Operations/ListSubscriptions.php b/src/Resources/Subscriptions/Operations/ListSubscriptions.php
index 5ee113a..44b3c6a 100644
--- a/src/Resources/Subscriptions/Operations/ListSubscriptions.php
+++ b/src/Resources/Subscriptions/Operations/ListSubscriptions.php
@@ -22,9 +22,9 @@ class ListSubscriptions implements HasParameters
      * @param array<SubscriptionStatus>                $statuses
      */
     public function __construct(
-        private readonly ?Pager $pager = null,
+        private readonly Pager|null $pager = null,
         private readonly array $addressIds = [],
-        private readonly ?CollectionMode $collectionMode = null,
+        private readonly CollectionMode|null $collectionMode = null,
         private readonly array $customerIds = [],
         private readonly array $ids = [],
         private readonly array $priceIds = [],
diff --git a/src/Resources/Subscriptions/Operations/PreviewUpdateSubscription.php b/src/Resources/Subscriptions/Operations/PreviewUpdateSubscription.php
index 5402016..fb7c6e8 100644
--- a/src/Resources/Subscriptions/Operations/PreviewUpdateSubscription.php
+++ b/src/Resources/Subscriptions/Operations/PreviewUpdateSubscription.php
@@ -26,15 +26,15 @@ class PreviewUpdateSubscription implements \JsonSerializable
     public function __construct(
         public readonly string|Undefined $customerId = new Undefined(),
         public readonly string|Undefined $addressId = new Undefined(),
-        public readonly string|null|Undefined $businessId = new Undefined(),
+        public readonly string|Undefined|null $businessId = new Undefined(),
         public readonly CurrencyCode|Undefined $currencyCode = new Undefined(),
         public readonly \DateTimeInterface|Undefined $nextBilledAt = new Undefined(),
-        public readonly SubscriptionDiscount|null|Undefined $discount = new Undefined(),
+        public readonly SubscriptionDiscount|Undefined|null $discount = new Undefined(),
         public readonly CollectionMode|Undefined $collectionMode = new Undefined(),
-        public readonly BillingDetails|null|Undefined $billingDetails = new Undefined(),
-        public readonly null|Undefined $scheduledChange = new Undefined(),
+        public readonly BillingDetails|Undefined|null $billingDetails = new Undefined(),
+        public readonly Undefined|null $scheduledChange = new Undefined(),
         public readonly array|Undefined $items = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
         public readonly SubscriptionProrationBillingMode|Undefined $prorationBillingMode = new Undefined(),
         public readonly SubscriptionOnPaymentFailure|Undefined $onPaymentFailure = new Undefined(),
     ) {
diff --git a/src/Resources/Subscriptions/Operations/UpdateSubscription.php b/src/Resources/Subscriptions/Operations/UpdateSubscription.php
index 52919d8..f332e8e 100644
--- a/src/Resources/Subscriptions/Operations/UpdateSubscription.php
+++ b/src/Resources/Subscriptions/Operations/UpdateSubscription.php
@@ -26,15 +26,15 @@ class UpdateSubscription implements \JsonSerializable
     public function __construct(
         public readonly string|Undefined $customerId = new Undefined(),
         public readonly string|Undefined $addressId = new Undefined(),
-        public readonly string|null|Undefined $businessId = new Undefined(),
+        public readonly string|Undefined|null $businessId = new Undefined(),
         public readonly CurrencyCode|Undefined $currencyCode = new Undefined(),
         public readonly \DateTimeInterface|Undefined $nextBilledAt = new Undefined(),
-        public readonly SubscriptionDiscount|null|Undefined $discount = new Undefined(),
+        public readonly SubscriptionDiscount|Undefined|null $discount = new Undefined(),
         public readonly CollectionMode|Undefined $collectionMode = new Undefined(),
-        public readonly BillingDetails|null|Undefined $billingDetails = new Undefined(),
-        public readonly null|Undefined $scheduledChange = new Undefined(),
+        public readonly BillingDetails|Undefined|null $billingDetails = new Undefined(),
+        public readonly Undefined|null $scheduledChange = new Undefined(),
         public readonly array|Undefined $items = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
         public readonly SubscriptionProrationBillingMode|Undefined $prorationBillingMode = new Undefined(),
         public readonly SubscriptionOnPaymentFailure|Undefined $onPaymentFailure = new Undefined(),
     ) {
diff --git a/src/Resources/Transactions/Operations/CreateTransaction.php b/src/Resources/Transactions/Operations/CreateTransaction.php
index 258914b..82587f8 100644
--- a/src/Resources/Transactions/Operations/CreateTransaction.php
+++ b/src/Resources/Transactions/Operations/CreateTransaction.php
@@ -26,16 +26,16 @@ class CreateTransaction implements \JsonSerializable
     public function __construct(
         public readonly array $items,
         public readonly StatusTransaction|Undefined $status = new Undefined(),
-        public readonly string|null|Undefined $customerId = new Undefined(),
-        public readonly string|null|Undefined $addressId = new Undefined(),
-        public readonly string|null|Undefined $businessId = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly string|Undefined|null $customerId = new Undefined(),
+        public readonly string|Undefined|null $addressId = new Undefined(),
+        public readonly string|Undefined|null $businessId = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
         public readonly CurrencyCode|Undefined $currencyCode = new Undefined(),
         public readonly CollectionMode|Undefined $collectionMode = new Undefined(),
-        public readonly string|null|Undefined $discountId = new Undefined(),
-        public readonly BillingDetails|null|Undefined $billingDetails = new Undefined(),
-        public readonly TransactionTimePeriod|null|Undefined $billingPeriod = new Undefined(),
-        public readonly Checkout|null|Undefined $checkout = new Undefined(),
+        public readonly string|Undefined|null $discountId = new Undefined(),
+        public readonly BillingDetails|Undefined|null $billingDetails = new Undefined(),
+        public readonly TransactionTimePeriod|Undefined|null $billingPeriod = new Undefined(),
+        public readonly Checkout|Undefined|null $checkout = new Undefined(),
     ) {
     }
 
diff --git a/src/Resources/Transactions/Operations/ListTransactions.php b/src/Resources/Transactions/Operations/ListTransactions.php
index b15b723..bd95a88 100644
--- a/src/Resources/Transactions/Operations/ListTransactions.php
+++ b/src/Resources/Transactions/Operations/ListTransactions.php
@@ -25,17 +25,17 @@ class ListTransactions implements HasParameters
      * @param array<Origin>            $origins
      */
     public function __construct(
-        private readonly ?Pager $pager = null,
-        private readonly ?DateComparison $billedAt = null,
-        private readonly ?CollectionMode $collectionMode = null,
-        private readonly ?DateComparison $createdAt = null,
+        private readonly Pager|null $pager = null,
+        private readonly DateComparison|null $billedAt = null,
+        private readonly CollectionMode|null $collectionMode = null,
+        private readonly DateComparison|null $createdAt = null,
         private readonly array $customerIds = [],
         private readonly array $ids = [],
         private readonly array $includes = [],
         private readonly array $invoiceNumbers = [],
         private readonly array $statuses = [],
         private readonly array $subscriptionIds = [],
-        private readonly ?DateComparison $updatedAt = null,
+        private readonly DateComparison|null $updatedAt = null,
         private readonly array $origins = [],
     ) {
         if ($invalid = array_filter($this->customerIds, fn ($value): bool => ! is_string($value))) {
diff --git a/src/Resources/Transactions/Operations/PreviewTransaction.php b/src/Resources/Transactions/Operations/PreviewTransaction.php
index 93c4a7f..ab472a8 100644
--- a/src/Resources/Transactions/Operations/PreviewTransaction.php
+++ b/src/Resources/Transactions/Operations/PreviewTransaction.php
@@ -21,14 +21,14 @@ class PreviewTransaction implements \JsonSerializable
      */
     public function __construct(
         public readonly array $items,
-        public readonly string|null|Undefined $customerId = new Undefined(),
-        public readonly string|null|Undefined $addressId = new Undefined(),
-        public readonly string|null|Undefined $businessId = new Undefined(),
+        public readonly string|Undefined|null $customerId = new Undefined(),
+        public readonly string|Undefined|null $addressId = new Undefined(),
+        public readonly string|Undefined|null $businessId = new Undefined(),
         public readonly CurrencyCode|Undefined $currencyCode = new Undefined(),
         public readonly CollectionMode|Undefined $collectionMode = new Undefined(),
-        public readonly string|null|Undefined $discountId = new Undefined(),
-        public readonly string|null|Undefined $customerIpAddress = new Undefined(),
-        public readonly AddressPreview|null|Undefined $address = new Undefined(),
+        public readonly string|Undefined|null $discountId = new Undefined(),
+        public readonly string|Undefined|null $customerIpAddress = new Undefined(),
+        public readonly AddressPreview|Undefined|null $address = new Undefined(),
         public readonly bool|Undefined $ignoreTrials = new Undefined(),
     ) {
     }
diff --git a/src/Resources/Transactions/Operations/UpdateTransaction.php b/src/Resources/Transactions/Operations/UpdateTransaction.php
index a35bf87..f77a9c2 100644
--- a/src/Resources/Transactions/Operations/UpdateTransaction.php
+++ b/src/Resources/Transactions/Operations/UpdateTransaction.php
@@ -24,17 +24,17 @@ class UpdateTransaction implements \JsonSerializable
      */
     public function __construct(
         public readonly StatusTransaction|Undefined $status = new Undefined(),
-        public readonly string|null|Undefined $customerId = new Undefined(),
-        public readonly string|null|Undefined $addressId = new Undefined(),
-        public readonly string|null|Undefined $businessId = new Undefined(),
-        public readonly CustomData|null|Undefined $customData = new Undefined(),
+        public readonly string|Undefined|null $customerId = new Undefined(),
+        public readonly string|Undefined|null $addressId = new Undefined(),
+        public readonly string|Undefined|null $businessId = new Undefined(),
+        public readonly CustomData|Undefined|null $customData = new Undefined(),
         public readonly CurrencyCode|Undefined $currencyCode = new Undefined(),
         public readonly CollectionMode|Undefined $collectionMode = new Undefined(),
-        public readonly string|null|Undefined $discountId = new Undefined(),
-        public readonly BillingDetails|null|Undefined $billingDetails = new Undefined(),
-        public readonly TransactionTimePeriod|null|Undefined $billingPeriod = new Undefined(),
+        public readonly string|Undefined|null $discountId = new Undefined(),
+        public readonly BillingDetails|Undefined|null $billingDetails = new Undefined(),
+        public readonly TransactionTimePeriod|Undefined|null $billingPeriod = new Undefined(),
         public readonly array|Undefined $items = new Undefined(),
-        public readonly Checkout|null|Undefined $checkout = new Undefined(),
+        public readonly Checkout|Undefined|null $checkout = new Undefined(),
     ) {
     }
 
diff --git a/src/ResponseParser.php b/src/ResponseParser.php
index 0c0a4d1..9ccb61e 100644
--- a/src/ResponseParser.php
+++ b/src/ResponseParser.php
@@ -10,7 +10,7 @@
 
 class ResponseParser
 {
-    private ?array $body = null;
+    private array|null $body = null;
 
     /**
      * @throws ApiError When the API response contains errors
diff --git a/tests/Utils/ReadsFixtures.php b/tests/Utils/ReadsFixtures.php
index a210f6a..3bfb982 100644
--- a/tests/Utils/ReadsFixtures.php
+++ b/tests/Utils/ReadsFixtures.php
@@ -14,7 +14,7 @@ public static function readJsonFixture(string $fixture): array
         return json_decode(self::readRawJsonFixture($fixture, $basePath), true, 512, JSON_THROW_ON_ERROR);
     }
 
-    public static function readRawJsonFixture(string $fixture, string $basePath = null): string
+    public static function readRawJsonFixture(string $fixture, string|null $basePath = null): string
     {
         if (! $basePath) {
             [$caller] = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 1);