Hi Kay,
If you 'reversed' the customer receipt from Bank Reconciliation, then AR transactions would be unaffected, and you would have to manually handle the paid invoices, such as posting an AR cash entry against the invoice(s) with a negative payment amount - provided that the invoices have not been cleared to History.
If you used 'NSF Processing' to reverse the customer receipt, then transactions are created in order to reverse the payment from the customer invoices, even if those invoices are in History. You don't have to generate NSF Fees in order to perform this processing.
_________________________
Regards,
Softrak Tech Support