Dynamics NAV - Auto Pay invoices and send balance to an account. Payment Invoices are automatically paid when prepayment invoices are generated.

Payment Method Setup - If you define a balancing account, the system will auto pay and apply gl entries to offset all transactions using that payment method, and send them to the balancing account specified.

If you notice all of your Invoices automatically generating and applying to payments, it is because there is a balancing account defined on your payment method.