The default rule

If a US person who was required to file Form 3520 dies before filing, the executor or administrator of the decedent's estate is responsible for filing the return on the decedent's behalf for the year(s) the obligation existed.

This is the same general rule that applies to Form 1040 for a deceased taxpayer. The estate steps into the shoes of the deceased filer.

The form mechanics

The executor files Form 3520 marking the filer's name as the deceased's name and adding "Deceased" + date of death after the name. Example:

John Smith, Deceased — January 14, 2025

The executor signs the form in their capacity as executor:

[Signature] Jane Smith, Executor of the Estate of John Smith

Attach a copy of the executor's appointment papers (letters testamentary or letters of administration from probate court) on first filing. The IRS keeps that on file for future correspondence.

Which year(s) does the estate file for

The estate files Form 3520 for:

Any prior tax year the decedent was required to file but did not (subject to applicable statutes of limitations).
The decedent's final tax year (the partial year through date of death).

For prior years where the decedent did not file but should have, the late-filing penalty potentially applies. The estate can file a reasonable-cause statement explaining the delay if the decedent's pre-death circumstances justify it.

What if the decedent already filed for all prior years

Then the estate may have nothing to do for Form 3520. The estate's own activities (probate distributions to heirs, foreign-trust transactions related to the decedent's estate, etc.) generate their own filings, but those are typically handled by the heirs receiving the bequests — not by the decedent's estate filing in its own name.

The bequest from the deceased — who reports

If the decedent died and bequeathed money to a US-person heir, the heir reports the bequest on their own Form 3520 Part IV — the decedent (or the decedent's estate) does not report it.

So you have two completely separate Form 3520 obligations:

The decedent's executor files for the decedent's own foreign-gift receipts (if any) during the decedent's lifetime that were not yet reported.
The US-person heir files for the bequest they received from the decedent (if the decedent was a foreign person and the bequest was > $100,000).

These are separate filings, often in separate tax years, often by different people.

A worked example

Background:

George was a US citizen who received a $150,000 gift from his foreign father in 2024 and failed to file Form 3520 for 2024.
George died in 2025.
George's foreign father died in 2025.
The foreign father's estate left $400,000 to George's daughter Sarah (US citizen).

Required filings:

For George's 2024 unreported gift: George's executor files a late Form 3520 for tax year 2024 reporting the $150,000 gift from George's foreign father. Reasonable-cause statement attached (death is generally accepted as reasonable cause if filed promptly after appointment).
For Sarah's 2025 bequest from her foreign grandfather: Sarah files Form 3520 Part IV for tax year 2025 reporting the $400,000 bequest. Sarah's filing has nothing to do with George's filing. Sarah files in her own name.
George's executor may also need to file George's final Form 1040 and possibly an estate income tax return (Form 1041) — separate from the Form 3520 questions.

What if there is no executor

If no executor or administrator has been appointed, an heir or other person responsible for the decedent's property can file as a "personal representative" of the decedent under the IRS's general rules. The IRS accepts a probate court appointment or a state-law equivalent.

In rare cases (small estate, no probate, no formal appointment), an heir can file with a written statement explaining their authority to act on the decedent's behalf. Get a CPA's help if this applies — the rules are state-specific.

Statute of limitations

For an unfiled Form 3520, there is no statute of limitations until the return is filed. The estate can be liable for the penalty indefinitely — the IRS can assess at any time.

Filing the late return starts the standard 3-year statute on the late-filed return (and the 6-year extended statute if the IRS argues substantial omission).

So the estate's interest is in filing promptly even for old years — filing the late return starts the clock running.

Our app

We do not have a special "filing for deceased" workflow. The executor signs up with their own credentials, enters the decedent's information as the filer (name + "Deceased" notation + date of death), and signs as executor. The questionnaire flow is otherwise the same.

For complex multi-year unreported filings or estates with foreign trusts involved, talk to a CPA — these situations need professional review.

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.

Filing Form 3520 for a Deceased Relative