If you are in an Installment Agreement and find that you could easily be paying more per month you should consider doing so, for by increasing your payment you will pay off the Agreement early and save interest.  You do not have to renegotiate a new Installlment Agreement, although you can if you wish.  Instead, you can add whatever amount you want to your monthly payment. For example, if you are currently paying $200 per month, you can voluntarily pay $500 instead of $200 per month.  This additional amount can change each month.  Please keep in mind; however, that you will need to pay at least $200 each month.  In other words, last month’s surplus payment does not create a credit for this month’s payment.