How Many Years of Back Taxes Does an Expat Need to File?

How many years of back taxes an expat needs to file depends on the route. Under the Streamlined Foreign Offshore Procedures it is the 3 most recent overdue tax returns and 6 most recent overdue FBARs. Outside that program, IRS policy normally asks for six years of returns. By law, every unfiled year stays open. Those three numbers are all correct at once, which is why the answers people find online disagree. This guide explains where each one comes from and how to tell which applies to you.

How many years of back taxes does an expat have to file?

An expat with a non-willful history files three years of returns and six years of FBARs under the Streamlined Foreign Offshore Procedures. An expat who cannot or does not use that program should expect to file six years of returns. No rule of law caps the number, because an unfiled year never closes.

It helps to see the answer as three layers, from the strict legal position down to what the IRS actually asks for.

Layer	Years	Where it comes from	Who it applies to
The law	Every year a return was required and not filed	No assessment time limit runs until a return is filed (IRS: Time IRS can assess tax)	Everyone, in theory
IRS enforcement policy	Normally six years of returns	Policy Statement 5-133, applied in Internal Revenue Manual 4.12.1	Late filers outside a special program
Streamlined Foreign Offshore Procedures	3 tax returns and 6 FBARs	IRS terms of the program	Expats who meet the non-residency test and certify non-willful conduct
Relief Procedures for Certain Former Citizens	6 returns: the year of expatriation and the 5 before it	IRS terms of the procedures	People who have already given up citizenship and meet the tax and net worth limits
Delinquent FBAR Submission Procedures	The FBAR years that were missed	IRS terms of the procedures	Expats who filed returns and paid the tax but missed the FBAR

Most Americans in the UK who have fallen behind end up in the third row. The rest of this article works through each row so you can place yourself.

What the law says: no time limit on an unfiled year

The legal starting point is the least comfortable one. The IRS normally has 3 years after a return was due, including extensions, to assess more tax. That clock only starts when a return is filed. The IRS states that when a required return is not voluntarily filed, it can assess tax at any time, and that preparing a Substitute for Return on your behalf does not start the 3-year limit either. Only your own filed return does.

So an American who moved to London in 2012 and never filed has, in law, an open year for every year since 2012 in which their worldwide income was over the filing threshold. Whether a return was required is tested on gross income before the foreign earned income exclusion, and IRS Publication 54 adds that net self-employment earnings of $400 or more require a return whatever the total.

This is the real reason to file at all. Filing is what starts the clock and eventually closes the year. An expat who files three years under the Streamlined procedures closes those three years in the ordinary way and relies on IRS practice, not on a statute, for the years before them.

What IRS policy says: the six-year rule

The figure of six years comes from IRS Policy Statement 5-133, which governs how far back the IRS enforces the filing of delinquent returns. Internal Revenue Manual 4.12.1, the examiners' manual for nonfiled returns, puts it in one sentence: the enforcement period is not to be more than six years.

That sentence is a default, and the manual is clear that it can move in either direction with managerial approval. The factors an examiner weighs are:

• the taxpayer's prior history of noncompliance;
• the existence of income from illegal sources;
• the effect on voluntary compliance;
• the anticipated revenue compared with the time and effort required; and
• any special circumstances of the taxpayer or the industry.

Two points follow. First, the six-year rule is an instruction to IRS staff. It is not a statute of limitations and a taxpayer cannot enforce it. Second, it describes what the IRS will normally demand, which makes it the sensible measure of "caught up" for an expat filing outside any program: six years of returns, filed in the normal way for each year.

What a late return costs outside a program

Late returns filed under the six-year practice carry the ordinary penalties. The failure to file penalty is 5% of the unpaid tax for each month or part of a month the return is late, up to 25%. For a return due after December 31, 2025 that is more than 60 days late, the minimum penalty is $525 or 100% of the unpaid tax, whichever is less. Interest runs on top.

Because the penalty is a percentage of unpaid tax, an expat whose UK tax fully covers the US bill through the foreign tax credit often has no failure to file penalty at all. The exposure is elsewhere: in the information returns. A late Form 5471 for a UK company, a late Form 3520 for a foreign trust or a missing Form 8938 carries its own penalty that does not depend on tax due. The IRS says of late international information returns that "penalties may be assessed in accordance with existing procedures," although a reasonable cause statement can be attached, as its delinquent international information return procedures explain.

What the Streamlined procedures say: 3 years of returns and 6 years of FBARs

The Streamlined Foreign Offshore Procedures replace the six-year practice with a shorter, defined package. The IRS terms require, for each of the most recent 3 years for which the US tax return due date (or properly applied for extended due date) has passed, a delinquent or amended return with all required information returns, and for each of the most recent 6 years for which the FBAR due date has passed, any delinquent FBARs.

In exchange, the IRS says the taxpayer will not be subject to failure-to-file and failure-to-pay penalties, accuracy-related penalties, information return penalties or FBAR penalties, unless a later examination finds fraud or willful conduct. You pay the tax and statutory interest shown on the three returns. That waiver of information return penalties is what makes three years under Streamlined more valuable than six years outside it for anyone with a UK company, trust or sizeable foreign assets.

The price of admission is eligibility. You must:

1. Meet the non-residency requirement. In at least one of the most recent three years you had no US abode and were physically outside the United States for at least 330 full days.
2. Have been non-willful. The IRS defines that as conduct due to negligence, inadvertence or mistake, or a good faith misunderstanding of the law. You certify it under penalty of perjury on Form 14653. Our guide to the non-willful certification covers how that statement should be written.
3. Not be under examination. If the IRS has started a civil examination of any of your years, the program is closed to you.
4. Hold a valid taxpayer identification number. For a US citizen that means a Social Security number.

Returns filed this way are not audited automatically, but the IRS says they may be selected under its normal audit processes. For the mechanics of the submission, see our Streamlined Foreign Offshore Procedures guide.

Which years count if you file in late 2026?

The three return years and six FBAR years are fixed by the date you submit. Each year is tested the same way: has its due date, or a properly requested extended due date, already passed?

You submit	Tax returns	FBARs
October 4 to October 15, 2026, with no extension requested for 2025	2023, 2024, 2025	2019 to 2024, with the 2025 FBAR filed on time by October 15
October 16, 2026 until the 2026 return comes due in 2027	2023, 2024, 2025	2020 to 2025

The 2025 return was due April 15, 2026, with an automatic 2-month extension to June 15, 2026 for Americans living abroad under Publication 54. The 2025 FBAR was due April 15, 2026 with an automatic extension to October 15, 2026. Anyone who properly extended their 2025 return beyond those dates should check the position before fixing the years; our Streamlined Filing Procedures 2026 article sets out the full timeline.

The window rolls forward. A package prepared for 2023 to 2025 and mailed after the 2026 return falls due would cover the wrong three years, so prepare for the date you will actually send it.

Refunds run on a different clock: 3 years, then gone

Old years are asymmetric. Tax you owe on an unfiled year stays collectable with no time limit. Money the IRS owes you does not. The IRS says in its guidance on filing past due tax returns that a return claiming a refund of withholding or estimated tax must be filed within 3 years of the return due date.

For an expat this matters in two common situations. A parent who would have qualified for a refundable credit can only collect it for years still inside that 3-year window. And someone who had US tax withheld on a US pension, dividends or a short spell of US work loses that withholding for older years if no return was filed. A late return for an expired year is still accepted. It simply produces no check.

One more consequence of not filing applies to the self-employed. The same IRS page warns that self-employment income on an unfiled return is not reported to the Social Security Administration, so it earns no credits toward retirement or disability benefits.

Special cases that change the number

You missed only one or two years

If you filed regularly and slipped for a year or two, you do not need a program. File the missing returns as ordinary late returns. If only the most recent deadline was missed, our article on missing the October 15 deadline abroad covers the cost.

You filed returns but not FBARs

If the income from your foreign accounts was reported and taxed, use the Delinquent FBAR Submission Procedures. You file the late FBARs electronically through FinCEN's BSA E-Filing System, choose a reason for late filing and include a statement explaining it. The IRS says it will not impose a penalty where the income was properly reported and you have not already been contacted about those years. If you have never filed one before, start with filing an FBAR for the first time.

You have already given up citizenship, or plan to

Expatriation uses a five-year measure. Form 8854 asks you to certify tax compliance for the five tax years before the year you expatriate. The Relief Procedures for Certain Former Citizens, which the IRS offers with no stated end date, let a person who relinquished citizenship after March 18, 2010 file six years in total (the year of expatriation and the five before it) without tax or penalties, if their net worth is under $2 million and their aggregate tax for those six years is $25,000 or less. Our guide to Form 8854 and the exit tax explains what is at stake if the certification cannot be made.

You relied on the foreign earned income exclusion

The exclusion is an election, and late elections have conditions. The IRS page on choosing the foreign earned income exclusion allows it on a late return filed within one year of the original due date. After that it is still available if you owe no federal income tax once the exclusion is counted, or if you owe tax but file before the IRS discovers the failure and print the required statement at the top of Form 1040. In UK cases the foreign tax credit often removes the US tax without any election, which is one reason the choice between the two is made year by year in a back-filing project.

An illustrative example

Illustrative example: Maya is a US citizen who moved from Boston to London in 2015. She filed a US return for 2014 and nothing since. She is a salaried employee taxed through PAYE, holds a current account, a savings account and a workplace pension, and learned of her filing duty from her bank's FATCA letter. In law, every year from 2015 onward is open. Under IRS policy, a late filer would be expected to produce six years. Because Maya lives abroad and her failure was non-willful, she uses the Streamlined Foreign Offshore Procedures in November 2026 and files Forms 1040 for 2023, 2024 and 2025, FBARs for 2020 through 2025 and a signed Form 14653. The years 2015 to 2022 are not filed. Her UK tax on salary exceeds the US tax on it, so the foreign tax credit leaves little or nothing to pay, and no penalties apply. This is a simplified illustration, not advice for any specific person.

What people get wrong about how many years to file

• "The IRS can only go back six years." Six years is internal policy. The law allows assessment at any time for a year with no return.
• "Streamlined means six years of tax returns." The six is for FBARs. The program asks for three tax returns.
• "I should file every year I missed to be safe." Filing more years than the Streamlined terms require is not what the program asks for, adds cost and puts years on record that the IRS did not request. Whether older years should be addressed is a judgment for the specific facts.
• "I will just start filing from this year." Filing the current year only leaves the earlier years open and unresolved, and a later non-willful certification is harder to support once you have shown that you know the rules.
• "I owe nothing, so the years do not matter." No tax due removes the failure to file penalty. It does not remove FBAR or information return obligations, and it does not start the assessment clock.

How to decide how many years of back taxes to file

1. List every year since you last filed, and for each one whether your worldwide gross income was over the filing threshold for that year.
2. List the forms, not just the returns: FBAR, Form 8938, and anything for a company, trust, foreign fund or pension.
3. Test Streamlined eligibility: 330 days abroad in one of the last three years, a non-willful history, no IRS examination, a valid Social Security number.
4. If eligible, prepare three returns and six FBARs for the date you will submit, with Form 14653.
5. If not eligible, plan on six years of late returns with reasonable cause statements where information returns are late, or take advice first if there is any doubt about willfulness.
6. Check the refund window for any year where the IRS would owe you money, and file those years before the 3-year limit passes.
7. File on time from now on. Every program assumes it.

How we help

US/UK Cross Border Tax is a firm of US CPAs and UK tax advisers working as one team, with offices in London, Manchester, New York and San Francisco. We work out how many years of back taxes an expat needs to file before anything is prepared, test Streamlined eligibility against your actual history, and then prepare the returns, FBARs and certification as one consistent submission. Where the IRS has already made contact, our tax controversy team takes over. Many of the people we help are Americans living in the UK or accidental Americans who learned of the rules years after they applied. To talk through your own years, contact us.