Where to Mail Form 3520 and 3520-A, and What Goes in the Envelope

Mailing and courier addresses

The P.O. box is the address in the Form 3520 instructions and the Form 3520-A instructions. The street address comes from the IRS list of submission processing center street addresses for private delivery services, which says to use a center’s street address only for the returns that center processes. Ogden is the center for Forms 3520 and 3520-A. Both pages change from time to time, so check them each filing season.

Keep it separate from the Form 1040

Form 3520 is an information return with its own filing address. It is not an attachment to the income tax return, so:

• Don’t staple it to a paper Form 1040 or put it in the same envelope. The Form 1040 goes to the address in its own instructions; Form 3520 goes to Ogden.
• Don’t wait for the e-filed 1040. An e-filed return can’t carry Form 3520. Mail Form 3520 on paper by its own due date.
• Extensions carry over. If the client filed Form 4868, check line 1k on Form 3520 and enter “1040”. You don’t need to include a copy of the Form 4868. See how to extend Form 3520.

Form 3520 can’t be e-filed, but it can be signed electronically. See can Form 3520 and 3520-A be e-filed?

Proof of timely mailing

Under IRC § 7502, a properly addressed return with enough postage is treated as filed on the postmark date. For a paper return, that rule is the whole timeliness case, so send it in a way you can prove:

• USPS certified or registered mail. Have the receipt postmarked at the counter and keep it in the client file.
• A designated private delivery service. The timely-mailing rule covers only the carriers and service levels on the IRS’s list of designated private delivery services. A carrier’s other services, such as ground delivery, may not be on it. Check the list before shipping and keep the carrier’s receipt showing the date it accepted the package.
• Ordinary first-class mail gives no record of the mailing date if the envelope is lost.

What goes in the envelope

The instructions are strict: only a complete Form 3520 is considered timely filed, and it is complete only if all required attachments are included. Include each item that applies:

Leave out: workpapers, the income tax return, the Form 4868, and your own checklists. Keep them in the client file. The instructions don’t prescribe an order for the pages. Putting Form 3520 on top, with attachments following in the order of its Parts, keeps the package easy to review.

Attaching a substitute Form 3520-A

When the foreign trust doesn’t file Form 3520-A, the U.S. owner prepares a substitute and attaches it to their own Form 3520. It is not mailed separately and is due with the Form 3520, including extensions.

1. Check the “Substitute Form 3520-A” box at the top of the Form 3520-A.
2. Have the U.S. owner sign it. The Form 3520-A instructions say: “A substitute Form 3520-A must be signed by the U.S. owner. The U.S. owner’s name and taxpayer identification number (TIN) must be provided on the ‘Title’ line of the signature box.”
3. Include its statements. The substitute includes the Foreign Grantor Trust Owner Statement (pages 3 and 4) and Beneficiary Statement (page 5).
4. Answer line 22 “No” on Form 3520 and attach the substitute behind the Form 3520.
5. Furnish the statements. Send copies of the Owner and Beneficiary Statements to the trust’s U.S. owners and U.S. beneficiaries by the Form 3520 due date.

See the substitute Form 3520-A walkthrough for completing the form itself.

One envelope per return

Forms 3520, 3520-A, and the Form 7004 for a Form 3520-A all go to the same Ogden P.O. box, but each one goes in its own envelope:

• A trust’s standalone Form 3520-A, filed by the trustee, is mailed on its own by its own deadline: the 15th day of the 3rd month after the trust’s year ends (March 15 for a calendar-year trust), or September 15 if extended. Don’t hold it for the owner’s Form 3520.
• A Form 7004 for a Form 3520-A is mailed on its own by March 15. See Form 3520-A is due March 15.
• Each Form 3520 goes in its own envelope. Clients who file separate Forms 3520 mail them separately; a joint Form 3520 is one return.
• A substitute Form 3520-A is the exception: it travels attached to the owner’s Form 3520.

Late filings

The IRS’s delinquent international information return submission procedures say that for Forms 3520 and 3520-A, reasonable-cause statements will be considered before a penalty is assessed. They ask filers to write “Reasonable Cause Statement attached” on the top of the first page of the form, and attach the statement to the return.

Returns filed under the streamlined filing compliance procedures follow those procedures’ own labeling and mailing instructions instead. Compare the two routes in late Form 3520: streamlined versus delinquent procedures, and see the reasonable cause guide for what the statement should cover.

Before you seal it

• Every signature line is signed and dated: the filer on Form 3520, the U.S. owner on a substitute Form 3520-A, and the preparer section.
• Every attachment in the table above that applies is in the envelope.
• Line 1j or 1k is checked if an extension or the June 15 date is relied on.
• The late-filing notation is on page 1 if a reasonable-cause statement is attached.
• A complete copy of everything mailed is in the client file.
• The postmarked receipt or carrier receipt is in the client file.

Agena’s print-ready package

Agena prepares the paper return and separates what you mail from what you keep:

• Form 3520: the download holds the Form 3520 with its required statements in one PDF to print and mail, plus workpapers and a mailing checklist, both marked “KEEP”. The checklist lists the attachments the return needs, the Ogden address, and a reminder that a courier needs the street address.
• Late Form 3520 (Part IV): when you prepare a reasonable-cause statement, it is added at the end of the Form 3520 PDF and page 1 is marked “Reasonable Cause Statement attached”.
• Substitute Form 3520-A: prepared in the Form 3520-A workspace, started from the Form 3520, at no extra charge. Add its PDF behind the Form 3520 when you assemble the envelope.
• Form 3520-A: the form with every Owner and Beneficiary Statement, separate copies of each statement to send, and the Form 7004 extension.
• Optional e-signatures: clients can sign from a phone or computer. The signed PDF is then printed and mailed; the return is still filed on paper.

Frequently asked questions

Where do I mail Form 3520?

By U.S. mail, to Internal Revenue Service Center, P.O. Box 409101, Ogden, UT 84409. By a designated private delivery service, to Internal Revenue Submission Processing Center, 1973 Rulon White Blvd., Ogden, UT 84201. Check the IRS instructions and the IRS street-address list each season.

Do I attach Form 3520 to my Form 1040?

No. Form 3520 is filed separately, on paper, at its own Ogden address, even when the Form 1040 is e-filed. If the Form 1040 was extended, check line 1k on Form 3520.

Can I send Form 3520 by courier?

Yes, if the carrier and service level are on the IRS list of designated private delivery services. Ship to the Ogden street address, because couriers can’t deliver to the P.O. box, and keep the carrier’s receipt.

Sources and filing references

This article uses the December 2025 Instructions for Forms 3520 and 3520-A and IRS.gov pages reviewed in October 2026. Check them again before filing.

• IRS Instructions for Form 3520
• IRS Instructions for Form 3520-A · Local instructions PDF
• IRS street addresses for private delivery services
• IRS designated private delivery services
• IRS delinquent international information return submission procedures
• IRC § 7502