Specify a negative A/R payment for the customer with the same check number. Because
the check has already been used for this customer, you must add a one or zero to the
end of the original check number.
Distribute the negative amount to the invoices that were originally
paid.
Note: If the original payment was distributed as an open payment to the customer's
A/R journal, then distribute the negative amount the same way.
Create a zero-amount invoice (for example, 0.00) and post it to
the customer's A/R journal.
Reapply the open positive payment to the zero-amount invoice.
Reapply the open negative payment to the zero-amount invoice.
Post the payments to zero them out on the customer's A/R journal.