If you owe money on your tax return and forgot to include a check with your filing, it is important for you to send the payment immediately. Include your social security number or taxpayer identification number, whichever you used on your tax return, on all correspondence with the IRS or your state department of revenue. This is how the agencies identify you, and it will help them match up your payment with your return.
Electronic payment is the fastest way to get the taxing agency your payment. If you are near or past the tax deadline, this will help you prevent or reduce interest on your late payment. The IRS accepts electronic payments on federal taxes through its e-file website. Using electronic payment, you can pay your taxes with a credit or debit card. Some methods may incur processing fees. You can also pay by phone with a credit or debit card.
Mail your check or money order payment to the same IRS processing center where you sent your return for federal income taxes. Include a form 1040-V, which is the payment voucher form, available for download from the IRS website. Fill in the form and include it with your check. Also write your social security number, a daytime phone number and the year and name of the form to which the payment applies. For example, if you are mailing the check for your 2010 federal income taxes in 2011, write "2010 form 1040" on your check. State tax agencies may have similar forms, so check your state's Department of Revenue website for payment voucher forms.
Paper payments take time to send, process and be credited to your account. You will be responsible for any late fees or interest payments that accrue until the payment is credited. Even if you originally intended to pay by check, consider changing to payment by phone or an electronic method if you are near your payment deadline. Even if you are charged a processing fee, it will likely be less than the fees for late payment.
Keep good records of your payment, including saving the electronic payment receipt or a mailing receipt from paper payments. This is your proof of payment in case the tax agency does not receive your payment due to mail or electronic errors. Watch your bank account or check with your credit card company to see when the payment is deducted from your account. If it is not deducted within the time you expect, call the tax agency to inquire about your options.