When you delete a customer payment, it's removed from the invoice it was applied to. If the invoice was closed, it becomes an open invoice again.
To delete a customer payment
Open the invoice the payment was applied to (Sales menu > Invoices > click the invoice). Need help finding an invoice?
In the Activity history at the bottom of the invoice, click the reference number for the payment you want to delete.
If the invoice was paid using a customer credit, click the reference number for the applied credit.
At the confirmation message, click Delete. If you've deleted the application of a credit, the credit will now be available to refund or be applied to another invoice. Learn about Processing customer returns.