Tax records have two sets of retention periods and no overlap between them. The American ones run from the date the return was filed. The British ones run from the end of the tax year the return covers.
Neither set is long. What catches people is the third category: documents that have to survive far beyond any published period because they establish what an asset cost.
In our practice, the expensive gap is never a missing receipt from four years ago. It is a purchase statement from 2009.
What is a tax record?
Anything supporting what a return says: payslips, statements, invoices, contracts and calculations. The return itself counts too, and both authorities suggest keeping copies of filed returns whatever period applies to the papers behind them.
How long does the IRS expect you to keep them?
Three years, in the ordinary case, and longer in specific situations. The IRS sets out the periods on its record keeping page, starting from the date the return was filed.
For a refund or credit claim made after filing, keep records for three years from filing or two years from paying the tax, whichever is later.
Worthless securities or a bad debt deduction extend the period to seven years.
The page also advises keeping copies of filed returns themselves, because they help with future returns and with any amendment.
| Situation | American period | Why it differs |
|---|---|---|
| Ordinary return, nothing unusual | 3 years | The standard limitation period |
| Claiming a refund or credit after filing | 3 years from filing or 2 from payment, whichever is later | Protects the claim |
| Worthless securities or bad debt deduction | 7 years | Longer window for those claims |
| Income omitted, more than 25% of gross income shown | 6 years | Extended assessment period |
| No return filed at all | Indefinitely | No period ever starts |
| Fraudulent return | Indefinitely | No limitation applies |
| Employment tax records | At least 4 years after the tax is due or paid | Separate rule for employers |
When does the six-year rule bite?
Where you left out income that belonged on the return, and the amount exceeds a quarter of the gross income shown. That is a mechanical test rather than a judgement about intent, and it matters more to Americans abroad than to most people, because foreign income is exactly what gets missed.
It matters more to Americans abroad than to most people, because foreign income is exactly what people miss.
A forgotten rental profit or an unreported foreign account can therefore extend the window on a whole year.
Keep six years where any part of your foreign position was uncertain at the time.
What does HMRC require?
Less time, measured differently. GOV.UK states that where a return goes in on or before the deadline, you should keep your records for at least 22 months after the end of the tax year the return is for.
Its record keeping guidance gives the worked example: file the 2024 to 2025 return online by 31 January 2026 and keep the records until at least the end of January 2027.
Where the return goes in late, keep them for at least 15 months after you sent it.
Business records carry their own requirements, which run longer than the personal ones.
Which documents outlive both sets of rules?
Anything establishing cost, ownership or basis. A completion statement from a house purchase matters whenever you eventually sell, and share or fund purchase confirmations do the same job. So does a probate valuation for anything inherited, however long ago it arrived.
Share and fund purchase confirmations do the same job, and so does a probate valuation for anything inherited.
Pension scheme documents matter decades later, particularly where a treaty position depends on the scheme qualifying.
No retention period covers those, because the event they matter for has not happened yet.
What about the dollar cost of things you own?
This is the cross-border version of the same problem, and it is the one we see most. An American measures gains in dollars, so a British asset needs a dollar cost fixed at the acquisition date.
Recording that figure at the time takes a minute. Reconstructing it fifteen years later means finding a historic exchange rate and defending the choice.
Write the dollar cost, the rate used and its source on the same page as the purchase document.
Our guide to exchange rate rules covers which rate is appropriate and why consistency matters.
Do you need paper?
No. HMRC's guidance is explicit that no rules govern the form records take, so paper, digital files and software records all qualify. Scans work perfectly well provided they stay legible and complete, and what really matters is whether you can retrieve them later.
Scans work perfectly well, provided they stay legible and complete.
What matters is retrievability. A folder nobody can search does the same job as no folder at all.
How should you organise tax records across two systems?
By calendar year, not by tax year. That single choice resolves most of the friction, because the American year is the calendar one and British documents can be filed into it.
Within each year, keep four groups: income, foreign accounts, assets and filings.
Add a one-page summary listing what was filed, when, and any position taken that needed explaining.
That summary lets you answer a question about the year without rereading everything in it.
What if a query arrives about an old year?
Answer from the file rather than from memory, and check first whether the period is even open. A query about a year outside the relevant window is worth querying itself.
Where records have gone, say so plainly and rebuild what you can from bank statements and third parties.
Both authorities handle incomplete records regularly. What neither deals with well is a changing story.
Our article on what happens in an HMRC enquiry sets out how the British process runs.
GOV.UK's Self Assessment deadlines fix when a year was due, which is where any question about an open period starts.
Does an unfiled year ever close?
No, and this is the most important line in the American guidance. Where nobody filed a return, keep the records indefinitely, because no limitation period ever starts running. A fraudulent return works the same way, which makes catching up far better than waiting.
A fraudulent return works the same way.
So an unfiled year stays open forever, which is the strongest practical argument for catching up rather than hoping.
Our article on Streamlined filing covers the route back for anyone with years missing.
What should you keep for foreign accounts?
The highest balance in each year, per account, with a statement supporting it. The reporting depends on that figure, and it is the one nobody writes down at the time.
Keep the account opening paperwork too, since it establishes ownership and signature authority.
Closed accounts still count for the year they existed, so download the final statement first.
Our comparison of Form 8938 and the FBAR explains which thresholds those balances feed.
The FBAR works from those peak balances, so the statement supporting each one is the document worth filing carefully.
Who else holds your tax records?
More parties than you might assume, and none of them indefinitely. Banks and platforms typically hold statements for a limited period, employers hold payroll data for their own retention window, and HMRC holds what you filed rather than what supported it.
So relying on a third party to still have something in ten years is a poor plan.
Download rather than bookmark. A link to an account you later close is worth nothing at all.
In our practice, the platform that has merged or closed is the single most common reason tax records cannot be rebuilt.
How long should a business keep tax records?
Longer than an individual, in both systems, and the rules differ by entity and by what the records cover. Employment tax records in America carry their own period of at least four years after the tax falls due or is paid.
British business records run to their own timetable too, separate from the personal one.
Anyone running a company through which they also draw income is therefore keeping two sets of tax records on two clocks.
Treat the longer period as the house rule and stop worrying about which applies.
What happens to records when someone dies?
They become the executor's problem, and they matter more than usual. An estate needs values at the date of death, and beneficiaries need those same figures for their own future gains.
So the family's tax records become the basis for calculations decades later.
Gather them while the estate is open rather than afterwards, and give each beneficiary a copy of what relates to them.
A retention policy that works
Keep everything for seven years by default. Seven years covers the ordinary American period, the extended one, and the British requirement several times over.
Keep cost and ownership documents permanently, in a separate folder you never clear.
Keep filed returns permanently as well. They are small and they answer most later questions.
That policy fits in three sentences and removes every judgement call about individual documents.
What tax records do you need before a move?
A move concentrates every gap at once, so gather before you go rather than after. Take payslips for the year, the P45 or P60, statements for every account as at the departure date, and valuations for anything you keep.
Those documents are ordinary to obtain while you live here and awkward from another continent.
Add the dollar cost of each asset you are keeping, recorded at the rate for its acquisition date.
That single folder answers most of what either authority will ask over the following decade.
Organising tax records, step by step
An afternoon once sets this up for good.
- Create one folder per calendar year, plus a permanent folder for cost and ownership papers.
- File British documents into the calendar year they fall in, not the tax year.
- Record the dollar cost and exchange rate for anything you buy, at the time.
- Note the highest balance of every foreign account each year.
- Keep a one-page summary in each year's folder of what was filed and when.
- Scan paper as it arrives rather than in an annual session.
- Clear folders older than seven years, leaving the permanent one untouched.
An illustrative example
Take an illustrative case. An American sells a London flat bought in 2011 and needs the dollar cost to work out the gain.
The completion statement survives. Nobody wrote down the exchange rate at the time. So the figure has to come from historic rates, and it has to stand up if questioned.
One line on the completion statement in 2011 would have made this a minute's work. The figures are illustrative; the missing line is entirely typical.
Common mistakes we see
First, keeping receipts and discarding contracts. The contract matters longer.
Second, filing by British tax year, which makes every American calculation harder. Third, closing an account without downloading the final statement.
Fourth, assuming an unfiled year eventually goes away. Fifth, keeping everything in an email inbox nobody can search.
Sixth, treating tax records as a filing chore rather than as evidence. The file exists to answer a question years later, from someone who was not there.
How US UK Tax Hub helps with tax records
We tell clients at the outset which documents matter for decades and which can go after seven years. That conversation takes ten minutes and saves the reconstruction work later.
Our US federal return service includes a summary of each year's positions, kept in a form that answers a query without reopening the whole file.
If a query has already arrived about an old year, send us what you have and we will work out what is actually needed.
