feat: add blurb about account balances

docs/account-management/billing.md

@@ -13,7 +13,6 @@ Brave Ads are available to be purchased via various different pricing models. By
 
 The pricing model is determined at the ad set level of the campaign and cannot be changed partway through a flight. In order to switch an ad set to a new pricing model, the original ad set must be paused, and a new one with the revised pricing model must be created. The original ad set will be billed according to the original pricing.
 
-
 ## Paying an invoice
 By default, invoices for managed campaigns are sent at the end of the monthly billing cycle for the calendar month. Payment is due within 30 days of receipt of the invoice. Brave may, at our discretion, require pre-payment for advertisers and campaigns prior to the launch of their campaign 
 
@@ -24,7 +23,7 @@ Both Managed Service and self-directed Brave Ads Manager campaigns can be paid b
 - If buying via Brave Ads Manager, you will be asked to pre-pay for your campaign by “topping-up” your account via Stripe.
 
 ## Paying with cryptocurrency
-Both Managed Service and self-directed Brave Ads Manager campaigns can be paid by credit card via Radom.
+Both Managed Service and self-directed Brave Ads Manager campaigns can be paid by using a crypto wallet via Radom.
 
 - If buying ads via Managed Service, simply let your account manager know you’d like to pay via cryptocurrency. Please note that we currently accept Basic Attention Token (BAT), USD Coin (USDC), and Tether USD (USDT) on the Ethereum blockchain.
 - If buying ads via Brave Ads Manager, you will be asked to pre-pay for your campaign by “topping-up” your account via Radom.
@@ -35,3 +34,19 @@ For New Tab Takeovers, advertisers that cancel within seven days of the campaign
 If working with our accounts and sales team, you can cancel your Search, Notifications, or Newsfeed ads campaigns at any time and will only be invoiced for the amounts spent up until the campaign was paused. 
 
 If you prepaid your campaign via our self-service option and wish to cancel your campaign early, please note that you’ll need to request a refund for any remaining balance by sending an email to [[email protected]](mailto:[email protected]).
+
+# Account balances
+
+Any leftover campaign budgets from pre-paid campaigns paid via Stripe or Radom will be transferred to your account balance for future campaigns. These funds are typically transferred within 24-48 hours, under the following two circumstances:
+
+### When a campaign reaches its end date
+
+If your campaign reaches its scheduled end date and there are remaining funds, the campaign status will update to "complete," and any leftover funds will be transferred to your account balance.
+
+### When a campaign is terminated manually
+
+To end your campaign immediately and transfer any remaining funds to your account balance, follow these steps:
+
+- Select the campaign.
+- Click "Edit."
+- Click "Close this campaign."