Specialist US UK Tax Services: What to Keep After Filing

After a streamlined filing, keep the certification, the returns, the FBARs and the proof of delivery permanently, and the evidence behind them for at least six to eight years. The familiar three-year rule assumes a clean domestic return with a closed assessment window. Where foreign accounts, information returns and reconstructed basis are involved, that assumption fails.

This is the part of the process almost nobody plans for. A submission under the Streamlined Foreign Offshore Procedures is assembled under pressure, often from records that were themselves reconstructed at cost from banks, custodians and pension administrators. The package goes to Austin, the payment clears, and the file gets archived somewhere between a laptop, an adviser's portal and a box in a Zurich or Kensington storeroom. Two years later the evidence chain is already fraying. Our Specialist US UK Tax Services practice at Jungle Tax exists precisely because reconstruction is expensive the first time and ruinous the second. What follows is the retention discipline we impose on our own client files, verified against current IRS and HMRC guidance.

Why the three-year instinct is wrong after a streamlined filing

The three-year rule most people carry in their heads is a summary of the general assessment period. The logic runs: the IRS has three years to assess, therefore after three years the records are dead weight. For a US-resident taxpayer with a W-2 and a mortgage, that is roughly right. For a dual-resident filer who has just completed a compliance catch-up, it is wrong in four separate ways.

• The window may never have opened cleanly. A late-filed information return can keep the assessment period open long after you assumed it had run.
• The IRS does not close your file. The Service is explicit that streamlined submissions are not acknowledged and do not end in a closing agreement. There is no certificate of completion to rely on.
• Two revenue authorities are watching. HMRC's discovery windows run on their own clock, and the offshore extension runs far longer than the standard four years.
• Your evidence was already thin once. The records that supported the streamlined package were, by definition, records you had failed to keep the first time. Losing them again removes your only defence.

The correct question is not "when may I destroy this?" It is "for how long could I be asked to prove this, and what happens if I cannot?" Those are different periods, and the second is almost always longer.

How long does the IRS actually say you must keep records?

The IRS publishes a period-of-limitations table that is the honest starting point, and it is more nuanced than the folk version. Its own guidance on how long you should keep records sets out the following:

• Three years where none of the extended situations apply.
• Three years from filing, or two years from paying the tax, whichever is later, where a refund or credit claim is made.
• Six years where income that should have been reported was omitted and it exceeds 25% of the gross income shown on the return.
• Seven years for a claim relating to worthless securities or a bad debt deduction.
• Indefinitely if no return was filed, and indefinitely if a fraudulent return was filed.
• Property records until the limitation period expires for the year in which the property is disposed of.
• Employment tax records for at least four years after the tax becomes due or is paid, whichever is later.

Read that list against a streamlined filer's history. "Indefinitely if you do not file a return" describes the very years that prompted the disclosure. "Property records until you dispose" describes a London flat bought in 2009 with basis reconstructed from a solicitor's completion statement. "Six years for a 25% omission" describes exactly the fact pattern that drives most offshore catch-ups. The extended rows are not exotic edge cases for this population. They are the base case.

The assessment window is not the retention window

How the standard three years breaks

Section 6501 gives the IRS three years from filing to assess. Three cross-border provisions extend that, and each one has a retention consequence.

First, a substantial omission of gross income exceeding 25% extends the period to six years. An overstatement of basis that produces the same effective omission can trigger it too, which matters when basis was reconstructed rather than documented contemporaneously.

Second, there is a separate six-year rule aimed squarely at offshore assets: where more than $5,000 of income attributable to a specified foreign financial asset is omitted, the six-year period applies regardless of whether the 25% threshold is crossed. For a filer with UK dividend income, an offshore bond or an investment account, $5,000 is a very low bar.

Third, and most severe, section 6501(c)(8) suspends the assessment period for the entire return where a required international information return was not filed. The period does not begin to expire until three years after the missing information is furnished. In practice this means a return year with a missing Form 5471 or Form 8938 stays open indefinitely until that form is delivered, and then for three further years.

Which forms trigger the suspension

The provision reaches the international information returns that cross-border private clients most often miss: Form 5471 for interests in foreign corporations, Form 8938 for specified foreign financial assets, Form 8621 for PFICs, Form 8865 for foreign partnerships, and Forms 3520 and 3520-A for foreign trusts and large foreign gifts. UK-resident founders and executives routinely hold at least one of these without realising it. A personal service company, an offshore bond, a UK unit trust or OEIC, a family trust established by a parent, or a legacy from a UK relative can each pull a return into the extended regime.

The practical retention rule follows mechanically. If your streamlined package included a late information return, the clock on that year restarts from the date it was furnished. Diarise that date, keep the proof of delivery, and count three years forward from it, not from the original filing deadline.

Provisions with no expiry at all

Two categories never expire. Fraudulent returns and unfiled returns leave the assessment period permanently open. A streamlined filer has, by definition, cured the second category for the years covered by the submission. The years outside the submission window are a different matter, and the certification you signed will have addressed them. That certification is the document you will be asked to stand behind, which is why it belongs in permanent storage rather than a six-year folder.

What FinCEN requires you to keep for FBAR

The FBAR carries its own statutory retention rule, entirely separate from the income tax rules, and it catches people out. Per the IRS guidance on the Report of Foreign Bank and Financial Accounts, records supporting each reportable account must be kept for five years from the FBAR due date, and must show:

• the name in which the account is maintained;
• the account number or other designation;
• the name and address of the foreign financial institution;
• the type of account; and
• the maximum value of the account during the reporting period.

A filed FBAR copy or a set of bank statements can satisfy this if it carries those details. Two subtleties matter for a streamlined filer. The retention period runs from the due date, not from the date you actually filed the delinquent report, so a six-year catch-up filed in 2026 covers years whose statutory retention windows are at different stages. And the civil penalty assessment period for FBAR failures is longer than the retention period, which is the clearest example anywhere in this area of exposure outliving the mandated record-keeping. Keeping FBAR support for only the minimum five years is, on those facts, an unforced error.

The maximum-value figure is also the single hardest number to reconstruct after the fact. Institutions purge statement archives, private banks close, and platform migrations lose historic balances. If you did the work once to establish peak balances across six years, that workpaper is worth more than the statements themselves. Preserve the reconciliation, not just the raw source. If you are pressure-testing historic exposure, our FBAR penalty calculator is a useful sanity check on what those figures could have driven.

What does HMRC expect you to keep, and for how long?

The 22-month rule and the five-year rule

HMRC operates two headline periods, and which one applies to you depends on whether you carry on a trade, profession or business. GOV.UK guidance on how long to keep your pay and tax records states that where a return is filed on or before the deadline, records should be kept for at least 22 months after the end of the tax year the return is for. Where the return is filed late, the period is at least 15 months after the return was sent.

For the self-employed and for partnerships, the period is materially longer: at least five years after the 31 January submission deadline for the relevant tax year. HMRC's Compliance Handbook confirms this split between business and non-business taxpayers. The statutory obligation sits in section 12B of the Taxes Management Act 1970, and a penalty of up to £3,000 can be charged for each failure to keep or preserve adequate records, though HMRC states it pursues this only in the more serious cases such as deliberate destruction during an enquiry.

Why 22 months is dangerously short for a cross-border filer

Twenty-two months is the minimum you must keep records; it is not the period during which HMRC may ask about them. Discovery assessment time limits run to four years from the end of the tax year where the taxpayer has not been careless, six years where behaviour was careless, and twenty years where it was deliberate. Critically for this readership, an extended limit of up to twelve years applies to offshore matters and offshore transfers irrespective of carelessness, covering income tax, capital gains tax and inheritance tax.

So a UK-resident American who has just made a US disclosure, and whose UK return may need corresponding correction, is potentially answerable to HMRC for twelve years on the offshore elements while being obliged to retain records for only 22 months. That gap is the whole argument for a bespoke retention policy rather than a statutory-minimum one.

Where records were lost

GOV.UK guidance for the self-employed is refreshingly practical about destroyed or missing records: do your best to provide figures, and tell HMRC whether they are estimated or provisional, with provisional figures replaced by actuals once available. That is a workable route, but it works far better when supported by a contemporaneous file note explaining what was lost, when, and what steps were taken to recover it. Reconstruct once, document the reconstruction, and never rely on being able to do it a third time.

US versus UK retention at a glance

Record or issue	United States / IRS position	United Kingdom / HMRC position
Baseline personal retention	3 years from filing where no extension applies	At least 22 months after the end of the tax year, if filed on time
Business or self-employment records	Employment tax records at least 4 years; general business records follow the limitation table	At least 5 years after the 31 January filing deadline
Late-filed return	Limitation period runs from actual filing	At least 15 months after the return was sent
Substantial omission	6 years where omitted income exceeds 25% of gross income shown	6 years from end of tax year where behaviour was careless
Offshore-specific extension	6 years where over $5,000 of income from a specified foreign financial asset is omitted	Up to 12 years for offshore matters and offshore transfers, regardless of carelessness
Deliberate or fraudulent conduct	No time limit on assessment	20 years from the end of the tax year
Missing information return	Assessment period for the whole return suspended until 3 years after the form is furnished	No direct equivalent; behaviour-based limits apply instead
Foreign account support	FBAR records for 5 years from the due date, with prescribed content	No standalone equivalent; support falls within general record-keeping duty
Asset basis and cost records	Keep until the limitation period expires for the year of disposal	Keep until the CGT position for the year of disposal is settled and out of time
Penalty for poor records	Evidential disadvantage rather than a standalone civil penalty	Up to £3,000 per failure under TMA 1970 s12B

The streamlined package itself: keep permanently, without exception

Everything above concerns supporting evidence. The submission is different. The IRS states plainly on its streamlined filing compliance procedures page that receipt of the returns will not be acknowledged and the process will not culminate in a closing agreement, that submissions may be selected for audit under existing selection processes, and that accuracy and completeness may be verified against information received from banks, financial advisers and other sources.

Translated: your own file is the only proof the submission ever happened, and third-party data may be tested against it years later. Hold the following permanently, in a single indexed set:

• The signed certification (Form 14653 for the foreign offshore procedures, or Form 14654 for the domestic version), including every narrative draft if the narrative evolved.
• Complete copies of all delinquent or amended returns as submitted, with every schedule and attachment.
• All FBARs as accepted, with the BSA E-Filing acknowledgement identifiers.
• Courier tracking and signed proof of delivery, since these packages are filed on paper.
• Payment evidence: cheque images, EFTPS confirmations, wire advices, and any interest computation.
• The non-willfulness evidence bundle: correspondence, adviser opinions, contemporaneous notes, medical or personal circumstances relied on, and anything establishing when you learned of the obligation.
• Residency proof relied on for the foreign offshore stream: passport pages, visas, residence permits, leases, HMRC records.
• The engagement file and adviser correspondence documenting the reasonableness of positions taken.

The non-willfulness bundle deserves particular emphasis. Non-willfulness is a state-of-mind conclusion supported by facts. Facts decay. A 2019 email from a UK bank saying "no US reporting is required for this account" is worth a great deal if you still have it and nothing at all if you do not.

Records that have no natural end date

Basis and acquisition cost

Basis records survive every ordinary retention rule because the relevant limitation period does not begin until the year of disposal. For a cross-border client this means completion statements on UK property, improvement expenditure, stamp duty land tax, share acquisition documents, EMI and option exercise records, gift and inheritance documentation, and any historic rebasing or valuation. Keep them until the disposal year is closed on both sides of the Atlantic, then keep the disposal computation for the extended period as well. Where the UK and US basis diverge, which is common after option exercises, non-dom rebasing or a change of functional currency, keep the reconciliation showing both figures. Our note on cross-border tax planning covers where those divergences typically arise.

Pensions, elections and treaty positions

UK pensions are the most under-documented item in the average American-in-London file. Retain scheme rules, joining documentation, annual statements, transfer histories, employer and employee contribution splits, any protection certificates, and the analysis supporting the treaty treatment adopted. Where a treaty-based position was disclosed, the disclosure and its supporting reasoning should sit with the permanent file. The same applies to elections that have continuing effect: mark-to-market and qualified electing fund elections on PFICs, currency elections, accounting method elections, and any election affecting the character of pension growth. An election is only as good as the evidence that it was validly made.

Foreign tax credit carryforwards

Excess foreign taxes carry forward for ten years. A refund claim attributable to foreign taxes generally has a ten-year window measured from the due date of the return for the year the taxes relate to. Together these mean the Form 1116 workpapers, the HMRC computations and the evidence of tax actually paid should be retained for at least thirteen years from the year the credit arose, not three. UK filers with large one-off events, an exit, a bonus year, a property disposal, frequently generate carryforwards that only become useful a decade later, and only if the underlying evidence still exists. Our US UK tax accountants maintain a rolling carryforward schedule for exactly this reason.

What a practical retention policy looks like

We recommend a three-tier policy. It is deliberately simple, because complicated policies are not followed.

Tier one: permanent

The full streamlined package as described above, all basis and acquisition records for assets still held, all pension and trust documentation, all elections, all treaty position analysis, prior-year returns for both jurisdictions as filed, and the reconstruction workpapers created during the disclosure. Prior-year returns themselves are compact; there is no meaningful cost to keeping every one you have ever filed, and considerable cost to being unable to produce one.

Tier two: long-cycle, eight to thirteen years

Bank and brokerage statements underlying reported income, foreign tax credit support, information return workpapers, rental property income and expense records, and the year-end valuations used for Form 8938 and FBAR maximum values. Eight years covers the six-year US omission windows with margin; thirteen covers the foreign tax credit carryforward tail. Where the year involved a late information return, extend to three years past the date that form was furnished.

Tier three: rolling minimum

Routine receipts, utility bills, small deductible expenses and correspondence with no evidential weight. Six years is ample, and aligns with the longer of the two ordinary statutory minimums on either side.

Format, custody and access

Four operational points determine whether the policy survives contact with reality:

• Digitise to searchable PDF with a fixed index. Name files by tax year, jurisdiction and document type. A folder of unnamed scans is not a record; it is a future reconstruction project.
• Hold your own copy. Adviser portals expire, firms merge, and engagement terminations rarely come with a full export. Take custody at the end of every engagement.
• Mind the GDPR and data-residency angle. UK data protection rules require a defensible reason for retaining personal data, including that of family members and employees. "Statutory tax retention period plus assessment window" is a defensible reason. Indefinite hoarding without a stated basis is not.
• Name a successor. If your executors cannot locate the streamlined file, your estate inherits the exposure without the defence. Estate exposure is a distinct problem set, addressed in our trusts and estate planning work.

What should you do if the records are already gone?

Reconstruction is possible but sequenced. Order IRS wage and income transcripts and account transcripts for the affected years, which will confirm what was filed and processed. Request statement archives from every institution before they purge; UK banks and platforms vary from six years to considerably less. Obtain HMRC records via a subject access request or your agent account. Retrieve Land Registry and conveyancing files for property basis. Approach pension administrators for scheme and contribution histories, which are often held longer than bank records. Then document the whole exercise in a memorandum recording what was recovered, what was not, and the methodology used for estimates. That memorandum becomes a permanent record in its own right.

Common mistakes we see after a streamlined filing

• Destroying at three years. Applying the domestic default to a file whose defining feature is foreign assets and late information returns.
• Keeping the returns but not the evidence. The return proves what you said; the evidence proves it was true.
• Losing the certification narrative drafts. The evolution of the narrative can matter as much as the final text.
• No proof of delivery. With no IRS acknowledgement, courier tracking is the only independent evidence the package arrived.
• Ignoring the UK side entirely. A US disclosure frequently implies a UK correction, and HMRC's offshore window runs far longer than the US default.
• Discarding pre-disclosure years. Years before the streamlined window may still be open where returns were never filed.
• Failing to diarise the restart date. Where a missing information return was cured, the three-year clock runs from that date, and almost nobody records it.

Full background on the disclosure process itself sits in our IRS streamlined filing resources, and the wider library of cross-border technical notes is in our guides.

Speak to us before you clear the file

If you completed a streamlined submission in the last several years and no longer know precisely what you hold, that is the moment to act, while institutions can still supply what is missing. We build retention schedules for private clients whose evidence had to be rebuilt once already, map each year against both the US assessment position and the HMRC discovery window, and take permanent custody of the disclosure file so it can be produced on demand a decade from now. To review your position in confidence, contact our cross-border team for a discreet consultation.