Once an invoice is sent, it can no longer be edited. If your customer sent more than the invoice total, you can record the difference in one of the ways below.
Close the original invoice
If your customer does not use VaultNow:
Open the invoice in Outgoing invoices.
Click Mark as paid.
In the Transaction field, select the incoming transaction that paid the invoice.
Confirm.
The invoice is marked as Paid and linked to that transaction.
Issue an invoice for the difference
You can create a new invoice for the extra amount, including one dated in the past:
Create a new outgoing invoice for the same customer.
Set the Invoice date to the day the payment arrived. The due date can't be earlier than the invoice date.
Send the invoice. Your customer will receive it by email.
Mark it as paid without selecting a transaction.
A transaction can be linked to only one invoice, so the new invoice is marked as paid without a link. Its payment date will be the day you mark it as paid.
Return the extra amount
If the overpayment was a mistake, you can send the difference back to your customer as a regular payment from the Payments page, or agree with them to count it toward their next invoice.
If your customer uses VaultNow
Invoices sent to customers who use VaultNow are closed by their payment and can't be marked as paid manually. Contact support if such an invoice needs to be sorted out.