Every time a new receipt is created, the user must enter the amount and select the payment type.
Go to Location Setup > General tab
Group: Accounting: Invoices and Receipts
Initialization of New Payment dialogue with default data basing on invoices due and unallocated deposits= Yes
With this setting enabled, the amount paid is automatically populated. The amount is calculated by the total of the outstanding invoices.
The payment type defaults to the payment type entered when the most recent receipt was created.
If any deposits exist, these will be allocated to the outstanding invoices first.