Only the US Postal Service can deliver to a PO Box. If you want to UPS or other private delivery services, the addresses are here: https://www.irs.gov/filing/submission-processing-center-street-addresses-for-private-delivery-service-pds The one you need is Ogden - Internal Revenue Submission Processing Center 1973 Rulon White Blvd. Ogden, UT 84201 More on reddit.com

Separate the federal and state returns - they need to be mailed separately. Some states do require a copy of your federal return or Form 1040. For the federal return, make sure you SIGN AND DATE the Form 1040, preferably with blue ink. Staple copies of W-2s and any 1099s with federal taxes withheld to the front of the Form 1040 to the left of Line 1. The rest of the federal return should be organized on order of the Seq number in the upper right corner, then place the 1040 on top and staple the stack in the upper left corner. Put in an envelope and mail to the address for your state: https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment It's taking the IRS about six months to process paper tax returns. If you want to have proof of when the IRS gets the return, send it certified mail and request a return receipt. More on reddit.com

See Where to File on the final page of the instructions to Form 1040 . (Generally, use the most recent instructions even if filing a prior year return, since they update for things like IRS offices moving and closing.) If you wish, you may include a check with the return. If you do, enclose Form 1040-V with your check and tax return, follow the instructions on how to write the check, and make sure to mail it to the address for "if your are enclosing a check..." You may also make a payment online instead of mailing a check. More on reddit.com

You have not enclosed a payment. A payment would be a check or money order. But I hope you realize that the account number on your tax form is for depositing a refund. It is not for paying any taxes you might owe. If you owe taxes, you either have to enclose a check or make a separate electronic payment on the IRS web site: https://www.irs.gov/payments/pay-personal-taxes-from-your-bank-account Writing bank account information on your tax return will NOT cause your taxes to be paid from that account. Also whats the best way to mail it? Put a postage stamp on it and deposit it in a mail receptacle. However, if this return is seriously late and you are facing a statute of limitations deadline soon, then take it to a Post Office and send it via Certified Mail. Don't lose the Certified Mail receipt. Do NOT let them talk you into Priority Mail, Express Mail, or a "Certificate of Mailing." Only Certified Mail and Registered Mail receipts are legal proof of filing. You would be wasting your money on the others. Also, be sure to SIGN AND DATE both your state and federal returns in the designated spaces, preferably in blue ink. Mail state and federal returns to separate addresses. Envelopes that weigh more than one ounce when they are full require extra postage. More on reddit.com