Head to the Billing section of your account and to the Billing information tab.
Below the Payment info, you can see the Prepaid balance section.
Here, you can see your current prepaid balance and add funds that can be used to pay for prepaid services, such as ordering domains and leads via API and potentially renewing subscriptions.
After clicking on the “Add funds” button, you’ll be redirected to the page where you can write the amount of credits to add to your balance. Those credits never expire.
If you delete the account and some balance is left unused, it won't be possible to refund it.