diff --git a/README.md b/README.md
index fbd4e43..7809716 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ This is a simple PHP library to help you deal with Europe's VAT rules.
 
 ## Installation
 
-[PHP](https://php.net) version 7.3 or higher with the CURL and JSON extension is required.
+[PHP](https://php.net) version 8.2 or higher with the CURL and JSON extension is required.
 
 For VAT number existence checking, the PHP SOAP extension is required as well.
 
diff --git a/composer.json b/composer.json
index d725f37..f288a31 100755
--- a/composer.json
+++ b/composer.json
@@ -10,13 +10,13 @@
     }
   ],
   "require": {
-    "php": ">=7.3",
+    "php": ">=8.2",
     "ext-curl": "*",
     "ext-json": "*"
   },
   "require-dev": {
-    "phpunit/phpunit": "^9.5",
-    "squizlabs/php_codesniffer": "^3.5"
+    "phpunit/phpunit": "^11.1",
+    "friendsofphp/php-cs-fixer": "^3.54"
   },
   "autoload": {
     "psr-4": {
@@ -35,5 +35,8 @@
   "suggest": {
     "ibericode/vat-bundle": "Symfony bundle for integrating this package",
     "ext-soap": "Needed to support VIES VAT number validation"
+  },
+  "scripts": {
+    "check-syntax": "find . -name '*.php' -not -path './vendor/*' -print0 | xargs -0 -n1 php --define error_reporting=-1 -l"
   }
 }
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 812ee72..fe907ce 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,31 +1,16 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit backupGlobals="false"
-         backupStaticAttributes="false"
-         beStrictAboutTestsThatDoNotTestAnything="true"
-         beStrictAboutOutputDuringTests="true"
-         bootstrap="vendor/autoload.php"
-         colors="true"
-         convertErrorsToExceptions="false"
-         convertNoticesToExceptions="false"
-         convertWarningsToExceptions="false"
-         failOnRisky="true"
-         failOnWarning="true"
-         processIsolation="false"
-         stopOnError="false"
-         stopOnFailure="false"
-         verbose="true"
->
-    <testsuites>
-        <testsuite name="VAT Test Suite">
-            <directory suffix="Test.php">./tests</directory>
-        </testsuite>
-    </testsuites>
-    <coverage processUncoveredFiles="true">
-        <include>
-            <directory suffix=".php">./src</directory>
-        </include>
-    </coverage>
-    <php>
-        <ini name="error_reporting" value="-1"/>
-    </php>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" backupGlobals="false" beStrictAboutTestsThatDoNotTestAnything="true" beStrictAboutOutputDuringTests="true" bootstrap="vendor/autoload.php" colors="true" failOnRisky="true" failOnWarning="true" processIsolation="false" stopOnError="false" stopOnFailure="false" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/11.1/phpunit.xsd" cacheDirectory=".phpunit.cache" backupStaticProperties="false">
+  <testsuites>
+    <testsuite name="VAT Test Suite">
+      <directory suffix="Test.php">./tests</directory>
+    </testsuite>
+  </testsuites>
+  <php>
+    <ini name="error_reporting" value="-1"/>
+  </php>
+  <source>
+    <include>
+      <directory suffix=".php">./src</directory>
+    </include>
+  </source>
 </phpunit>
diff --git a/src/Clients/IbericodeVatRatesClient.php b/src/Clients/IbericodeVatRatesClient.php
deleted file mode 100644
index 5247212..0000000
--- a/src/Clients/IbericodeVatRatesClient.php
+++ /dev/null
@@ -1,52 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Ibericode\Vat\Clients;
-
-use Ibericode\Vat\Period;
-
-class IbericodeVatRatesClient implements Client
-{
-    /**
-     * @throws ClientException
-     *
-     * @return array
-     */
-    public function fetch(): array
-    {
-        $url = 'https://raw.githubusercontent.com/ibericode/vat-rates/master/vat-rates.json';
-
-        $ch = curl_init();
-        curl_setopt($ch, CURLOPT_URL, $url);
-        curl_setopt($ch, CURLOPT_TIMEOUT, 6);
-        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
-        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
-        curl_setopt($ch, CURLOPT_MAXREDIRS, 2);
-        $body = (string) curl_exec($ch);
-        $status = (int) curl_getinfo($ch, CURLINFO_HTTP_CODE);
-        curl_close($ch);
-
-        if ($body === '' || $status >= 400) {
-            throw new ClientException("Error fetching rates from {$url}.");
-        }
-
-        return $this->parseResponse($body);
-    }
-
-    private function parseResponse(string $response_body): array
-    {
-        $result = json_decode($response_body, false);
-
-        $return = [];
-        foreach ($result->items as $country => $periods) {
-            foreach ($periods as $i => $period) {
-                $periods[$i] = new Period(new \DateTimeImmutable($period->effective_from), (array) $period->rates);
-            }
-
-            $return[$country] = $periods;
-        }
-
-        return $return;
-    }
-}
diff --git a/src/Countries.php b/src/Countries.php
index c89cf0f..cabf2b1 100644
--- a/src/Countries.php
+++ b/src/Countries.php
@@ -4,8 +4,6 @@
 
 namespace Ibericode\Vat;
 
-use DateTime;
-
 /**
  * Class Countries
  *
@@ -285,7 +283,41 @@ public function hasCountryCode(string $code): bool
      */
     public function getCountryCodesInEU(): array
     {
-        return ['AT', 'BE', 'BG', 'CY', 'CZ', 'DE', 'DK', 'EE', 'ES', 'FI', 'FR', 'GR', 'HU', 'HR', 'IE', 'IT', 'LT', 'LU', 'LV', 'MT', 'NL', 'PL', 'PT', 'RO', 'SE', 'SI', 'SK'];
+        return [
+            'AT', // Austria
+            'AX', // Aland islands => Finland
+            'BE', // Belgium
+            'BG', // Bulgaria
+            'CY', // Cyprus
+            'CZ', // Czechia
+            'DE', // Germany
+            'DK', // Denmark
+            'EE', // Estonia
+            'ES', // Spain
+            'FI', // Finland
+            'FR', // France
+            'GF', // French guiana => France
+            'GP', // Guadeloupe => France
+            'GR', // Greece
+            'HU', // Hungary
+            'HR', // Croatia
+            'IE', // Ireland
+            'IT', // Italy
+            'LT', // Lithuania
+            'LU', // Luxembourg
+            'LV', // Latvia
+            'MT', // Malta
+            'MQ', // Martinique => France
+            'NL', // Netherlands
+            'PL', // Poland
+            'PT', // Portugal
+            'RE', // Reunion => France
+            'RO', // Romania
+            'SE', // Sweden
+            'SI', // Slovenia
+            'SK', // Slovakia
+            'YT', // Mayotte => France
+        ];
     }
 
     /**
@@ -304,8 +336,7 @@ public function isCountryCodeInEU(string $code): bool
      * @return mixed Can return any type.
      * @since 5.0.0
      */
-    #[\ReturnTypeWillChange]
-    public function current()
+    public function current(): mixed
     {
         return current($this->data);
     }
@@ -316,8 +347,7 @@ public function current()
      * @return void Any returned value is ignored.
      * @since 5.0.0
      */
-    #[\ReturnTypeWillChange]
-    public function next()
+    public function next(): void
     {
         next($this->data);
     }
@@ -328,8 +358,7 @@ public function next()
      * @return mixed scalar on success, or null on failure.
      * @since 5.0.0
      */
-    #[\ReturnTypeWillChange]
-    public function key()
+    public function key(): mixed
     {
         return key($this->data);
     }
@@ -341,8 +370,7 @@ public function key()
      * Returns true on success or false on failure.
      * @since 5.0.0
      */
-    #[\ReturnTypeWillChange]
-    public function valid()
+    public function valid(): bool
     {
         return key($this->data) !== null;
     }
@@ -353,8 +381,7 @@ public function valid()
      * @return void Any returned value is ignored.
      * @since 5.0.0
      */
-    #[\ReturnTypeWillChange]
-    public function rewind()
+    public function rewind(): void
     {
         reset($this->data);
     }
@@ -363,8 +390,7 @@ public function rewind()
      * @param string $countryCode
      * @return bool
      */
-    #[\ReturnTypeWillChange]
-    public function offsetExists($countryCode)
+    public function offsetExists($countryCode): bool
     {
         return isset($this->data[$countryCode]);
     }
@@ -374,8 +400,7 @@ public function offsetExists($countryCode)
      * @return string
      * @throws \Exception
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($countryCode)
+    public function offsetGet($countryCode): mixed
     {
         if (!$this->offsetExists($countryCode)) {
             throw new Exception("Invalid country code {$countryCode}");
@@ -387,22 +412,18 @@ public function offsetGet($countryCode)
     /**
      * @param string $countryCode
      * @param string $name
-     * @return string
      * @throws \Exception
      */
-    #[\ReturnTypeWillChange]
-    public function offsetSet($countryCode, $name)
+    public function offsetSet($countryCode, $name): void
     {
         throw new Exception('Invalid use of Countries class');
     }
 
     /**
      * @param string $countryCode
-     * @return string
      * @throws \Exception
      */
-    #[\ReturnTypeWillChange]
-    public function offsetUnset($countryCode)
+    public function offsetUnset($countryCode): void
     {
         throw new Exception('Invalid use of Countries class');
     }
diff --git a/src/Period.php b/src/Period.php
index 3b59d59..9098589 100644
--- a/src/Period.php
+++ b/src/Period.php
@@ -17,11 +17,13 @@ class Period
 {
     private $effectiveFrom;
     private $rates = [];
+    private $exceptions = [];
 
-    public function __construct(DateTimeInterface $effectiveFrom, array $rates)
+    public function __construct(DateTimeInterface $effectiveFrom, array $rates, array $exceptions = [])
     {
         $this->effectiveFrom = $effectiveFrom;
         $this->rates = $rates;
+        $this->exceptions = $exceptions;
     }
 
     public function getEffectiveFrom(): DateTimeInterface
@@ -29,12 +31,28 @@ public function getEffectiveFrom(): DateTimeInterface
         return $this->effectiveFrom;
     }
 
-    public function getRate(string $level): float
+    public function getRate(string $level, ?string $postcode = null): float
     {
         if (!isset($this->rates[$level])) {
             throw new InvalidArgumentException("Invalid rate level: {$level}");
         }
 
-        return $this->rates[$level];
+        return $this->getExceptionRate($level, $postcode) ?? $this->rates[$level];
     }
+
+    private function getExceptionRate(string $level, ?string $postcode): ?float
+    {
+        if (!$postcode) {
+            return null;
+        }
+
+        foreach ($this->exceptions as $exception) {
+            if (preg_match('/^'.$exception['postcode'].'$/', $postcode)) {
+                return $exception[$level] ?? $exception[Rates::RATE_STANDARD];
+            }
+        }
+
+        return null;
+    }
+
 }
diff --git a/src/Rates.php b/src/Rates.php
index a98a10b..80bea98 100644
--- a/src/Rates.php
+++ b/src/Rates.php
@@ -38,7 +38,7 @@ class Rates
      * @param int $refreshInterval How often to check for new VAT rates. Defaults to every 12 hours.
      * @param Client|null $client The VAT client to use.
      */
-    public function __construct(string $storagePath, int $refreshInterval = 12 * 3600, Client $client = null)
+    public function __construct(string $storagePath, int $refreshInterval = 12 * 3600, ?Client $client = null)
     {
         $this->refreshInterval = $refreshInterval;
         $this->storagePath = $storagePath;
@@ -67,7 +67,11 @@ private function load(): void
     private function loadFromFile(): void
     {
         $contents = file_get_contents($this->storagePath);
-        $data = unserialize($contents, [
+        if ($contents === false || $contents === '') {
+            throw new Exception("Unserializable file content");
+        }
+
+        $data = @unserialize($contents, [
             'allowed_classes' => [
                 Period::class,
                 DateTimeImmutable::class
@@ -131,25 +135,26 @@ private function resolvePeriod(string $countryCode, DateTimeInterface $datetime)
     /**
      * @param string $countryCode ISO-3166-1-alpha2 country code
      * @param string $level
+     * @param ?string $postcode
      * @return float
      * @throws \Exception
      */
-    public function getRateForCountry(string $countryCode, string $level = self::RATE_STANDARD): float
+    public function getRateForCountry(string $countryCode, string $level = self::RATE_STANDARD, ?string $postcode = null): float
     {
         $todayMidnight = new \DateTimeImmutable('today midnight');
-        return $this->getRateForCountryOnDate($countryCode, $todayMidnight, $level);
+        return $this->getRateForCountryOnDate($countryCode, $todayMidnight, $level, $postcode);
     }
 
     /**
      * @param string $countryCode ISO-3166-1-alpha2 country code
      * @param DateTimeInterface $datetime
      * @param string $level
+     * @param ?string $postcode
      * @return float
      * @throws Exception
      */
-    public function getRateForCountryOnDate(string $countryCode, \DateTimeInterface $datetime, string $level = self::RATE_STANDARD): float
+    public function getRateForCountryOnDate(string $countryCode, \DateTimeInterface $datetime, string $level = self::RATE_STANDARD, ?string $postcode = null) : float
     {
-        $activePeriod = $this->resolvePeriod($countryCode, $datetime);
-        return $activePeriod->getRate($level);
+        return $this->resolvePeriod($countryCode, $datetime)->getRate($level, $postcode);
     }
 }
diff --git a/src/Validator.php b/src/Validator.php
index d276ba9..2e811dc 100644
--- a/src/Validator.php
+++ b/src/Validator.php
@@ -29,7 +29,7 @@ class Validator
         'GB' => '(\d{9}|\d{12}|(GD|HA)\d{3})',
         'HR' => '\d{11}',
         'HU' => '\d{8}',
-        'IE' => '([A-Z\d]{8}|[A-Z\d]{9})',
+        'IE' => '((\d{7}[A-Z]{1,2})|(\d[A-Z]\d{5}[A-Z]))',
         'IT' => '\d{11}',
         'LT' => '(\d{9}|\d{12})',
         'LU' => '\d{8}',
@@ -55,7 +55,7 @@ class Validator
      *
      * @param Vies\Client $client        (optional)
      */
-    public function __construct(Vies\Client $client = null)
+    public function __construct(?Vies\Client $client = null)
     {
         $this->client = $client ?: new Vies\Client();
     }
diff --git a/src/Vies/Client.php b/src/Vies/Client.php
index 67134aa..2b9ae44 100644
--- a/src/Vies/Client.php
+++ b/src/Vies/Client.php
@@ -43,6 +43,19 @@ public function __construct(int $timeout = 10)
      * @throws ViesException
      */
     public function checkVat(string $countryCode, string $vatNumber): bool
+    {
+        return (bool)$this->getInfo($countryCode, $vatNumber)->valid;
+    }
+
+    /**
+     * @param string $countryCode
+     * @param string $vatNumber
+     *
+     * @return object
+     *
+     * @throws ViesException
+     */
+    public function getInfo(string $countryCode, string $vatNumber): object
     {
         try {
             $response = $this->getClient()->checkVat(
@@ -55,7 +68,7 @@ public function checkVat(string $countryCode, string $vatNumber): bool
             throw new ViesException($e->getMessage(), $e->getCode());
         }
 
-        return (bool) $response->valid;
+        return $response;
     }
 
     /**
diff --git a/tests/Clients/ClientsTest.php b/tests/Clients/ClientsTest.php
index e3d2055..0f87972 100644
--- a/tests/Clients/ClientsTest.php
+++ b/tests/Clients/ClientsTest.php
@@ -2,18 +2,21 @@
 
 namespace Ibericode\Vat\Tests\Clients;
 
+use Ibericode\Vat\Clients\ClientException;
 use Ibericode\Vat\Clients\IbericodeVatRatesClient;
 use Ibericode\Vat\Clients\Client;
 use Ibericode\Vat\Period;
+use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
 
 class ClientsTest extends TestCase
 {
     /**
      * @group remote-http
-     * @dataProvider clientProvider
+     * @throws ClientException
      */
-    public function testClient(Client $client)
+    #[DataProvider('clientsProvider')]
+    public function testClient(Client $client): void
     {
         $data = $client->fetch();
         $this->assertIsArray($data);
@@ -22,7 +25,7 @@ public function testClient(Client $client)
         $this->assertInstanceOf(Period::class, $data['NL'][0]);
     }
 
-    public function clientProvider()
+    public static function clientsProvider(): \Generator
     {
         yield [new IbericodeVatRatesClient()];
     }
diff --git a/tests/CountriesTest.php b/tests/CountriesTest.php
index 85381bc..d97d13e 100644
--- a/tests/CountriesTest.php
+++ b/tests/CountriesTest.php
@@ -9,14 +9,14 @@
 
 class CountriesTest extends TestCase
 {
-    public function testIterator()
+    public function testIterator(): void
     {
         $countries = new Countries();
 
         $this->assertCount(249, $countries);
     }
 
-    public function testArrayAccess()
+    public function testArrayAccess(): void
     {
         $countries = new Countries();
 
@@ -27,35 +27,35 @@ public function testArrayAccess()
         $countries['FOO'];
     }
 
-    public function testArrayAccessWithInvalidCountryCode()
+    public function testArrayAccessWithInvalidCountryCode(): void
     {
         $countries = new Countries();
         $this->expectException(Exception::class);
         $countries['FOO'];
     }
 
-    public function testArrayAccessSetValue()
+    public function testArrayAccessSetValue(): void
     {
         $countries = new Countries();
         $this->expectException(Exception::class);
         $countries['FOO'] = 'bar';
     }
 
-    public function testArrayAccessUnsetValue()
+    public function testArrayAccessUnsetValue(): void
     {
         $countries = new Countries();
         $this->expectException(Exception::class);
         unset($countries['FOO']);
     }
 
-    public function testHasCode()
+    public function testHasCode(): void
     {
         $countries = new Countries();
         $this->assertFalse($countries->hasCountryCode('FOO'));
         $this->assertTrue($countries->hasCountryCode('NL'));
     }
 
-    public function testIsCodeInEU()
+    public function testIsCodeInEU(): void
     {
         $countries = new Countries();
         $this->assertFalse($countries->isCountryCodeInEU('FOO'));
diff --git a/tests/GeolocatorTest.php b/tests/GeolocatorTest.php
index 9f2c2ba..137ffdc 100644
--- a/tests/GeolocatorTest.php
+++ b/tests/GeolocatorTest.php
@@ -3,22 +3,23 @@
 namespace Ibericode\Vat\Tests;
 
 use Ibericode\Vat\Geolocator;
+use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
 
 class GeolocatorTest extends TestCase
 {
     /**
-     * @dataProvider provider
      * @group remote-http
      */
-    public function testClient($service)
+    #[DataProvider('servicesProvider')]
+    public function testService($service): void
     {
         $geolocator = new Geolocator($service);
         $country = $geolocator->locateIpAddress('8.8.8.8');
         $this->assertEquals('US', $country);
     }
 
-    public function provider()
+    public static function servicesProvider(): \Generator
     {
         yield ['ip2c.org'];
     }
diff --git a/tests/RatesTest.php b/tests/RatesTest.php
index 12e865b..f25a424 100644
--- a/tests/RatesTest.php
+++ b/tests/RatesTest.php
@@ -19,7 +19,7 @@ protected function setUp(): void
         }
     }
 
-    private function getRatesClientMock()
+    private function getRatesClientMock(): \PHPUnit\Framework\MockObject\MockObject
     {
         $client = $this->getMockBuilder(IbericodeVatRatesClient::class)
             ->getMock();
@@ -39,6 +39,17 @@ private function getRatesClientMock()
                     new Period(new \DateTimeImmutable('2019/01/01'), [
                         'standard' => 21.00,
                         'reduced' => 9.00,
+                    ], [
+                        [
+                            "name" => "Park Frankendael",
+                            "postcode" => "1097",
+                            "standard" => 0
+                        ],
+                        [
+                            "name" => "Park de Meer",
+                            "postcode" => "(1098|1099)",
+                            "standard" => 0
+                        ]
                     ])
                 ]
             ]);
@@ -53,6 +64,15 @@ public function testGetRateForCountry()
         $this->assertEquals(21.0, $rates->getRateForCountry('NL'));
     }
 
+    public function testGetRateForCountryAndPostcode()
+    {
+        $client = $this->getRatesClientMock();
+        $rates = new Rates('vendor/rates', 30, $client);
+        $this->assertEquals(0, $rates->getRateForCountry('NL', Rates::RATE_STANDARD, '1097'));
+        $this->assertEquals(0, $rates->getRateForCountry('NL', Rates::RATE_STANDARD, '1099'));
+        $this->assertEquals(0, $rates->getRateForCountry('NL', Rates::RATE_STANDARD, '1098'));
+    }
+
     public function testGetRateForCountryOnDate()
     {
         $client = $this->getRatesClientMock();
diff --git a/tests/ValidatorTest.php b/tests/ValidatorTest.php
index 1381327..64d78f8 100644
--- a/tests/ValidatorTest.php
+++ b/tests/ValidatorTest.php
@@ -3,6 +3,7 @@
 namespace Ibericode\Vat\Tests;
 
 use Ibericode\Vat\Validator;
+use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
 
 /**
@@ -12,9 +13,9 @@
 class ValidatorTest extends TestCase
 {
     /**
-     * @covers Validator::validateVatNumberFormat
+     * @coversXXX Validator::validateVatNumberFormat
      */
-    public function testValidateVatNumberFormat()
+    public function testValidateVatNumberFormat(): void
     {
         $valid = [
             'ATU12345678',
@@ -39,6 +40,8 @@ public function testValidateVatNumberFormat()
             'HU12345678',
             'HR12345678901',
             'IE1234567X',
+            'IE1X34567X',
+            'IE1234567XX',
             'IT12345678901',
             'LT123456789',
             'LU12345678',
@@ -78,6 +81,9 @@ public function testValidateVatNumberFormat()
             'HU1234567',
             'HR1234567890',
             'IE123456X',
+            'IE1X34567XX',
+            'IE12345678X',
+            'IE123456789',
             'IT1234567890',
             'LT12345678',
             'LU1234567',
@@ -113,16 +119,14 @@ public function testValidateVatNumberFormat()
         }
     }
 
-    /**
-     * @dataProvider validIpAddresses
-     */
-    public function testValidateIpAddressWithValid($value)
+    #[DataProvider('validIpAddresses')]
+    public function testValidateIpAddressWithValid($value): void
     {
         $validator = new Validator();
         $this->assertTrue($validator->validateIpAddress($value));
     }
 
-    public function validIpAddresses()
+    public static function validIpAddresses(): array
     {
         return [
             ['8.8.8.8'],
@@ -130,16 +134,14 @@ public function validIpAddresses()
         ];
     }
 
-    /**
-     * @dataProvider invalidIpAddresses
-     */
-    public function testValidateIpAddressWithInvalidValues($value)
+    #[DataProvider('invalidIpAddresses')]
+    public function testValidateIpAddressWithInvalidValues($value): void
     {
         $validator = new Validator();
         $this->assertFalse($validator->validateIpAddress($value));
     }
 
-    public function invalidIpAddresses()
+    public static function invalidIpAddresses(): array
     {
         return [
             ['0.8.8.8.8'],
@@ -148,18 +150,14 @@ public function invalidIpAddresses()
         ];
     }
 
-    /**
-     * @dataProvider validCountryCodes
-     */
-    public function testValidateCountryCodeWithValidValues($value)
+    #[DataProvider('validCountryCodes')]
+    public function testValidateCountryCodeWithValidValues($value): void
     {
         $validator = new Validator();
         $this->assertTrue($validator->validateCountryCode($value));
     }
 
-    /**
-     * @dataProvider invalidCountryCodes
-     */
+    #[DataProvider('invalidCountryCodes')]
     public function testValidateCountryCodeWithInvalidValues($value)
     {
         $validator = new Validator();
@@ -167,7 +165,7 @@ public function testValidateCountryCodeWithInvalidValues($value)
     }
 
 
-    public function validCountryCodes()
+    public static function validCountryCodes(): array
     {
         return [
            ['NL'],
@@ -177,7 +175,7 @@ public function validCountryCodes()
         ];
     }
 
-    public function invalidCountryCodes()
+    public static function invalidCountryCodes(): array
     {
         return [
             ['FOO'],