Short answer

The IRS does not publish a "Form 3520-X" or formal amended version. To amend Form 3520, you file a new corrected Form 3520 with the "Amended Return" box checked at the top of page 1, and mail it to the same IRS Ogden address.

When you should amend

The amount you reported was materially wrong (you found a missing transaction, or the FX rate was off by enough to change USD totals).
You missed a donor (you reported one $80,000 gift but forgot a $40,000 gift from a related donor that should have aggregated to $120,000).
You filed under Part IV but the situation actually involved a foreign trust and Parts I-III apply.
Donor information was wrong (wrong name, wrong country).
Date of receipt was wrong.

When you do NOT need to amend

The original Form 3520 had a typo that does not change any number (correct spelling later if asked).
You realized you also need to file FBAR or Form 8938 — those are separate forms, file them separately.
The IRS sent a letter asking for clarification — respond directly to the letter, do not file an amended Form 3520 unless they tell you to.

The mechanics

Pull up a blank Form 3520 PDF or use our app to generate a new one.
Check the "Amended Return" box at the top of page 1.
Fill in all the information correctly — not just the changed parts. The IRS treats your amended form as a complete replacement.
Sign and date under penalty of perjury.
Attach a one-paragraph cover letter on top explaining what you changed and why. Example: "I previously filed Form 3520 for tax year 2024 on March 20, 2025. I am filing this amended return because I omitted a $42,000 gift from a related donor that should have been aggregated. The corrected total reportable gift amount is $147,000."
Mail certified mail with return receipt to:

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

Keep your USPS receipt.

What about penalties on an amended return

If your original Form 3520 was timely but missed information, filing an amended return is generally not subject to the late-filing penalty — you filed something on time, and you are correcting it. The IRS would have a hard time arguing the original was effectively a failure-to-file.

If your original was an inadvertent under-report (e.g., you said $90,000 when the right number was $150,000), the IRS could theoretically argue the original was substantially incomplete and assess a penalty. In practice, voluntary amendments filed before an IRS examination usually avoid penalty.

If your original Form 3520 was late and you are now also amending it, the late-filing penalty is calculated based on when the original was filed, not when the amendment was filed. So amending a late return does not reset the clock.

Statute of limitations on amendments

The general rule is you have 3 years from the original filing date to amend most tax returns. Form 3520 has no income-tax impact for most filers (it is informational), so the 3-year rule is less mechanically relevant — but the IRS expects you to amend within a reasonable time of discovering the error. Waiting 5 years to amend something you found 4 years ago looks bad.

Tip — file the correct version the first time

The cheapest amendment is one you never have to file. Before mailing your original Form 3520:

Verify every donor name and country.
Verify each transaction date matches the actual receipt date, not the wire date.
Re-check the FX rate on each transaction — use the rate for the day you received the gift, not the day it was sent.
Aggregate gifts from related donors (parents, siblings, related entities).
Confirm the part of the form matches your facts (Part IV for individual gifts, Parts I-III for trust matters).

If you used our app, the FX rates and aggregation are handled for you — most amendments come from missing transactions or wrong donor information, which is human-entered.

3520file is software, not a CPA firm or law firm. We prepare IRS Form 3520 based on the facts you provide. For advice on your specific situation, talk to a tax attorney or CPA. The above is plain-English explanation, not tax advice.

How to Amend Form 3520 After You've Filed