Steps
Open the invoice
Go to Invoices and tap on the invoice you want to unmark as paid.
Open the actions menu
Tap the floating button ( ⋮ ) in the bottom right corner.
Tap 'Unmark As Paid'
Choose this option to remove the manual payment.
Confirm your decision
The invoice will now show as unpaid for both you and the customer.
Tips
Once unmarked, the invoice will return to awaiting payment status.
The previous payment info will no longer appear on the invoice link or PDF.
You can always Mark As Paid again later if needed.