To alter a customer's credit balance in Stripe, use the following steps:
Navigate to the customer's account in Stripe by using the search bar function to find the customer.
Ensure that the Overview tab is selected at the top of the screen.
Scroll down to the Invoice credit balance section and click "Adjust balance" on the right-hand side.
To credit, select the Credit "Adjustment type." Select Debit when wishing to deduct monies, then enter the amount to credit.
Add an optional note for the record.
When finished, click "Apply to credit balance." All changes are immediate.
If at any point in this guide, you seem to be unable to make the necessary changes in Stripe, you may need adjustments to your Stripe role. Please see the article Stripe Roles for more information.