When using the "Payment " Tab, Our Invoices & Estimates programs will automatically apply a payment to the oldest outstanding "due" invoice for a customer. It will do this for the oldest invoice until it is fully paid, then apply the remainder of the payment to the next-most outstanding "due" invoice until it is paid, and so on, until the payment is fully applied.
However, instead of having the program determine which invoices to "pay off" when a customer payment is made, you can specify a specific invoice or set of invoices to pay with the customer payment. This way, you can control where and when the payment is applied to the customer's account.
To do this, you want to use the column on the Payment Tab view's Invoice Listing called "Distribution". Here, you can click in the row of the invoice you want to pay in its "Distribution" column. When the cursor appears, enter the payment amount to apply, then hit the TAB key on your keyboard to tab to the next row. The "Apply Payment" button should be highlighted now about the Invoice Listing and if you click it, the amount you entered will be applied to that specific invoice.
Using this method, you can click in the "Distribution" column for any and all rows of invoices to pay and divide up a customer payment in any manner you wish.