In order to change payment method you dont have to inverse the invoice. You can do that directly with the already created invoice.
- Go to POS
- Click on the spy glass right next to "Order No:"
- Find the invoice
- Double-click on it in order to display it in POS
- Click on "OK" when you see the "Validation" message
- Click on "F4 Invoice"
- Click "OK" when you see the "Validation" message
- In order to delete the payment click on the red "X" signt right next to the "$" signt
- Choose "Yes" on the "Validation" and "Warning" messages
- Choose new payment method
NOTE: If your end of day has been already done that will affect your reports and accounting software.