Cancelling an Invoice on POS:
Go to Invoice Management
Key in staff pin and select Confirm
Select the invoice that you want to cancel from the list at left panel
Note: If the list is too long, you can search the invoice number or customer's name or phone numberSelect CANCEL INVOICE at the bottom right
Select YES to confirm cancelling the invoice
Key in the terminal pin, and select OK
Enter the void reason (it is a compulsory field)
Once done, tap OK to successfully cancel the invoice
Here's a step-by-step video guide: