Use Form 9465 to request a monthly installment plan if you cannot pay the full amount you owe shown on your tax return (or on a notice we sent you). Use Form 9465 to request a monthly installment agreement (payment plan) if you can't pay the full amount you owe shown on your tax return.A letter from the IRS will require some kind of response, perhaps even a payment or a payment arrangement. And you can't just sit on such letters. A payment plan, or "Installment Agreement", is an agreement a Taxpayer makes with the IRS to pay back taxes owed over an extended period. If you can't pay the full amount you owe, you can ask to make monthly installment payments. You can request a payment plan. Learn why you might receive a letter from the IRS, the various types of letters they send, and what steps to take if you receive one. Remove any check stub before sending. Do not mail cash with your return.