Writing off sales taxes after an invoice is paid
Use Customer Cash Receipt Entry to write off sales tax after an invoice is paid. For example, if a customer is nontaxable, but their invoice total included sales tax, you can write off the sales tax amounts and credit the correct tax accounts. Assuming the customer has already paid the invoice, minus the tax, the remaining amount on the invoice is the tax amount, which you will write off. This write off may be necessary if the customer does not submit their tax register number until after they have submitted payment. Ideally, you should also change their taxable status in Customer Setup to avoid write-offs in the future. You must have correct security in SA Operator Setup to write off cash receipts.
See Correcting invoices where the incorrect exemption certificate was applied.