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). Installment Payment Plan Request.Click here to request a payment plan online using MyTax Illinois. 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. You also can complete Form CPP-1, Payment Installment Plan Request, to request a payment installment plan. If you can't pay the full amount you owe, you can ask to make monthly installment payments. The 9465 form is rather short and only requires your personal information, the name and addresses of your bank and employer, the amount of tax you owe. Can't pay your Illinois state taxes in full? Consider an Installment Payment Plan. You may request a payment plan (including an installment agreement) using the OPA application.