I am trying to reverse payment on an invoice due to receipt of NSF check. Please advise.

If you have Adagio BankRec, this is easy because there is an NSF handling function.

Without BankRec, create a negative dollar amount cash entry and apply it to the same invoice(s) that were paid by the payment, as long as the invoice has not been cleared to History.

If the invoice and payment have been cleared to History then this makes things more difficult (without BankRec). You'll need to do Ledger journal entries to reverse the effects of the check, and essentially re-create and post the invoice(s) that were paid by the NSF payment. You can no longer effect the actual payment transaction once it has been cleared to history (without BankRec).