Each order keeps its total sale and every payment the customer made, so you always know how much is still due. You'll find them under Payments on the right side of the order (on a phone, near the top).

Add a Payment
- Open the order. An order without payments or a total sale doesn't show Payments: click Add… at the end of the right side and choose Payments.
- Enter the Total sale if it's not there yet. It's saved when you leave the field or press Enter.
- Click Add payment. The amount starts at what is still due.
- Change the amount and the date it was paid if needed, then click Add payment.
Amount due shows what is left to pay. Once the payments add up to the total sale, it says Paid in full and Add payment is hidden. The payments can't add up to more than the total sale.
Change or Remove a Payment
- Change the total sale: type the new amount. It can't be less than the payments.
- Change a payment: remove it and add it again with the right amount or date.
- Remove: point at the payment and click the trash icon. Click Undo in the message to bring it back.
See All Payments
The dashboard lists Recent Payments, and Reports > Order Payments shows the payments of all orders for the dates you choose.
Can see the payments but not change them? Your user group needs access to order payments: ask your admin.