post https://public.billsby.com/api/v1/rest/core//customers//refunds
Use this API request to refund an invoice for a customer. You can do a full or partial refund, up to the total amount of the invoice. If you want to sue the API to check the total refundable amount left on the invoice, you can use the Get Individual invoice API to get this information.
If the refund is successful, the API will return the amount left to refund on the invoice. If it was a partial refund this amount will show in unformatted amount, i.e. if the invoice amount is $10 and you refund 100, the total amount left to refund on the invoice will be $9.