Checks or money orders should be made payable to the United States Treasury.
Please provide your correct name, address, social security number, daytime
telephone number, tax year and form number on the front of your payment (never send cash!). If you are making a payment on a joint
return, provide the social security number that was listed first on the return.
If you have a balance due on your return, use Form 1040-V(PDF), Payment Voucher. Enclose your payment and Form
1040–V with your Federal tax return. Do not staple or otherwise
attach the payment or Form 1040–V to your return. Instead,
just put them loose in the envelope. If you make a payment in person at an
IRS office, keep the receipt as part of your records.
Never mail estimated tax payments with checks or money orders meant for
payment of current year Federal income tax. Mail your estimated tax payments separately, to the address shown in the Form 1040-ES(PDF).