At times you may receive a payment that is more than the balance due from the payer. Once you create a voucher for the payment, whatever you do not use will remain on the voucher as undistributed funds. Any time you like, you can apply undistributed funds in a new Credit entry.
After selecting the payer and Credit Type (check, in the example below), clicking the Check field will show any existing check vouchers with undistributed amounts. In this case, there is such a check, so we can select it and apply any or all of the available $100 instead of creating a new check voucher.
It works exactly the same way for other types of payments (Cash, Credit Card, or Other) .