You are correct. When opening an outstanding invoice from 'Open Invoice List', it does reflect the new tax rate but, if you go into 'Apply Payment' the amount reflects the original amount at the original tax rate. When viewing original invoices, if you do NOT press the 'Record' button, then the tax rate remains at the original amount. Also your taxable amount for taxable sales, in your "Accounting Report', will only reflect any new transactions since the new tax rate change.