Third Party Processor (Lockbox) / Form 1040-V Introduction A lockbox is a collection and processing service provided by a network of financial institutions that accelerates the flow of funds to the U.S. Treasury. Overview This commercial third-party processing takes place through a contract with the Internal Revenue Service (IRS) and the Financial Management Service (FMS) and involves the use of the Form 1040-V, Payment Voucher. Some balance due taxpayers must send their voucher, payment and sometimes their return to a designated location (a lockbox bank). Questions and Answers on Third Party Processor (Lockbox) Why does the IRS want me to use a payment voucher? The IRS is modernizing its payment system. The Form 1040-V, "Payment Voucher," is part of the modernization. If you have a balance due on your tax return, using the payment voucher will help the IRS process your payment more accurately and efficiently. Do I need to use the payment voucher? Yes. If you owe tax, send your tax return, payment voucher, and payment to the appropriate address indicated in the instructions or on IRS.gov. How do I prepare my payment when using the voucher? Make your check or money order payable to the United States Treasury. Don't send cash. If your name and address are not printed on your check or money order, print them so they can be easily read. Also, print your Social Security number (SSN), daytime telephone number, and "2021 Form 1040" on your check or money order. Double check to make sure that you have printed your SSN correctly and that it matches the one used on your income tax return. How do I fill out the payment voucher if it is not pre-printed? Line 1. Enter your social security number (SSN). If you are filing a joint return, enter the SSN shown first on your return. Line 2. If you are filing a joint return, enter the SSN shown second on your return. Line 3. Enter the amount you are paying by check or money order. Line 4. Enter your name(s) and address exactly as shown on your return. Please print clearly. How do I send in my payment, tax return and the payment voucher? Detach the payment voucher at the perforation. DO NOT attach the payment voucher or your payment to your tax return or to each other. Send your return, payment voucher and check to the appropriate address indicated in the instructions or on IRS.gov. What do I do if I have already mailed in my return without the payment? If you have already mailed your return, send your payment and the payment voucher to the appropriate address located in the instructions or on IRS.gov. Where do I get a payment voucher? You can get the form by calling the tax forms number, 1-800-829-3676. You can also pick one up at your local IRS office. Call them first, 1-800-829-1040, to make sure that the form is available and to check on hours of service. I filed my return electronically. Where do I send my payment voucher and payment? Do I also need to send a copy of my return that was filed electronically? Send your payment voucher and payment to the lockbox address associated with the service center where your return was filed. If you have filed your return electronically, do not send a paper copy of your return with your payment.