After opening the invoice details, click on the Add Payment button in the Invoice Actions list. In the opened window fill out the details and click on the Create Payment button to confirm.
Dentaltap - Create Invoice Payment
Type - a payment type, set to Cash by default;
Amount - payment amount, can be full invoice amount, or partial payment;
Date/Time - date and time, when the payment was collected.
Group - a custom tag (group) for analytics purposes, for example, if you collect payments via credit cards by several POS systems, you can specify the device id as a group. And in analytics, you will see collections for each POS separately.
Once you created a payment, you can see it in the Payments List under the Invoice.