Form 3520 mailing address and deadline

Form 3520 is one of the few IRS forms that still only exists on paper. Mail it to the wrong place or a day late and you are in penalty territory for a form that owed no tax. Here is the address, the date, and the proof you keep.

Where to mail it

By U.S. Postal Service

Internal Revenue Service Center
P.O. Box 409101
Ogden, UT 84409

By FedEx, UPS or DHL (couriers cannot deliver to a P.O. Box)

Internal Revenue Submission Processing Center
1973 Rulon White Blvd.
Ogden, UT 84201

Addresses move. Before you seal the envelope, check "When and Where To File" in the IRS Form 3520 instructions and the IRS list of street addresses for private delivery services. The packet the wizard builds prints both addresses and that link on the cover sheet.

Mail Form 3520 on its own. Do not staple it to your Form 1040, do not put it in the same envelope as your return, and do not send it to the address where you mail a payment.

When it is due

Form 3520 is due when your income tax return is due, including any extension:

Your situation	Due date
Living in the U.S., no extension	April 15 of the following year
Living outside the U.S. (and main place of business abroad) on April 15	June 15 — automatic two-month extension
Filed Form 4868 (or 2350) for your return	October 15

If the date falls on a weekend or a federal holiday, the deadline moves to the next business day. The IRS does not grant a separate extension for Form 3520; your return's extension carries over.

A common misunderstanding: the Form 4868 extension applies only if you actually filed it. Filing your 1040 in October without an extension does not stretch Form 3520.

How to prove you mailed it on time

The IRS "timely mailed, timely filed" rule means the postmark date is your filing date. So:

1. Use USPS Certified Mail with Return Receipt, or a tracked service from a designated private delivery service. Ordinary first-class mail gives you no proof.
2. Keep the receipt with the postmark, and later the delivery confirmation, in the same folder as your copy of the form.
3. Photograph or scan the signed form before mailing. The IRS does not send an acknowledgment for Form 3520.

What goes in the envelope

• Form 3520, signed and dated (both spouses for a joint form), with your SSN or ITIN written in.
• A short cover letter stating the tax year and that Part IV is enclosed. Not required, but it helps a processing clerk route a form that owes no tax.
• If you are filing late: your reasonable cause statement, attached directly behind the form. See late filing and penalty abatement.

Nothing else. No bank statements, no gift letters, no check.

Missed it?

If the money arrived in a previous year and you are only now learning about the form, file as soon as you can with a reasonable cause statement. The penalty clock runs per month, so weeks matter.

Let the wizard do the paperwork

The Form 3520 wizard prints the right address for your carrier, computes your due date from your extension status, generates a cover letter, and gives you an .ics calendar file with a 30-day and 7-day reminder. The deadline calendar is free; the packet is $79.

Self-prepared information return. Not tax or legal advice. Not affiliated with the IRS.