The Worldwide Disclosure Facility is HMRC's standing route for disclosing any UK tax liability that relates wholly or partly to an offshore issue — overseas income, offshore assets, or activities carried on abroad. You notify HMRC through the Digital Disclosure Service, receive a Disclosure Reference Number, and then have 90 days to gather the information, calculate the tax, interest and penalties, and file the disclosure. It offers no guaranteed penalty reduction and no immunity from prosecution.
For American citizens and Green Card holders living in Britain, the word "offshore" is misleading in a way that matters. Your offshore assets are usually your American ones: the brokerage account in New York, the rental property in Florida, the IRA, the 401(k) distribution. If those produced income that never reached a UK Self Assessment return, this is the facility that applies — and the penalty regime behind it reaches 200% of the tax.
Why Americans in the UK end up here
The typical case is not evasion. It is a US citizen who moved to London, registered for Self Assessment, declared their UK salary properly, and never thought to declare the dividends accumulating in a US brokerage account — because those had already been reported to the IRS, and it seemed obvious that American income was America's business.
Once UK tax resident and taxed on the arising basis, you are taxable in the UK on worldwide income and gains. The US-UK treaty and foreign tax credits usually prevent double taxation, but they do not remove the obligation to declare. In many cases the additional UK tax after credit relief is modest — and the penalties for not declaring are not.
The second common route in is the nudge letter. HMRC receives account data automatically from over a hundred jurisdictions under the Common Reporting Standard, and the United States supplies data under the reciprocal side of FATCA. A letter that says HMRC has "information about overseas income" is not a fishing expedition.
How the Worldwide Disclosure Facility works, step by step
The mechanics are set out in HMRC's guidance on how to make a disclosure using the Worldwide Disclosure Facility. The process has two distinct stages, and the gap between them is where the pressure sits.
Stage one is notification through the Digital Disclosure Service, giving your personal and National Insurance details. HMRC acknowledges and issues a Disclosure Reference Number, which must be quoted on everything afterwards. Stage two is the disclosure itself.
From acknowledgement you have 90 days to complete stage two. Where the case is genuinely complex — a corporate structure, a trust, a contested point of legal interpretation — you can request a further 90 days, giving up to 180 in total. That extension is requested at the point of notification, not on day 85.
- Notify HMRC through the Digital Disclosure Service and obtain a Disclosure Reference Number.
- Establish your behaviour category — this drives how many years you must disclose and the penalty range.
- Reconstruct the income and gains for every affected year, in sterling, with exchange rates evidenced.
- Calculate tax, interest and a self-assessed penalty, and state the offshore jurisdictions involved by country code.
- Submit within 90 days of acknowledgement, then pay — or arrange time to pay — at the same time.
The 90-day clock is the trap, not the deadline
Ninety days sounds ample. It is not, because the clock starts when you notify, and almost nobody notifies with the underlying work already done. Reconstructing six, twelve or twenty years of US brokerage activity — dividends, interest, realised gains, each translated to sterling at the right rate — takes longer than most people expect, and the American custodian's historic statements are frequently only available for the last ten years.
The practical rule is to do the analysis before notifying, not after. There is no penalty for spending three months reconstructing your position privately and then notifying with a near-complete disclosure. There is a great deal of difficulty in notifying first and discovering on day 60 that a 2013 account cannot be reconstructed at all.
The one situation that reverses this logic is a nudge letter with its own response deadline. There, notify within the stated window and request the complex-case extension at the same time.
Behaviour decides everything: how many years you disclose
There is no fixed number of years in the WDF. The period you must disclose is driven by your behaviour, because behaviour determines HMRC's assessment time limits.
Broadly, an innocent error carries a four-year window, carelessness six years, and deliberate behaviour twenty. Offshore matters involving income tax and capital gains tax sit on an extended twelve-year window for non-deliberate cases, introduced to give HMRC longer to work through internationally sourced data. Liabilities stretching beyond twenty years require you to contact HMRC separately rather than using the standard route.
Self-classifying is the single most consequential judgement in the whole exercise, and it is not a judgement to make optimistically. Declaring yourself careless when the facts read as deliberate invites HMRC to reject the disclosure and open an investigation; declaring yourself deliberate when you were merely careless costs you fourteen extra years and a far higher penalty.
The penalty regime: where 200% comes from
Offshore penalties are not the ordinary domestic percentages. They are geared to the jurisdiction the income came from, on the theory that hiding money somewhere opaque is worse than hiding it somewhere transparent.
Territories are grouped into three categories. Category 1 territories exchange information with the UK automatically and carry a maximum penalty of 100% of the potential lost revenue. Category 2 territories exchange on request, at up to 150%. Category 3 territories share nothing, at up to 200%. HMRC's factsheet on penalties for offshore non-compliance sets out how the categories apply.
The United States is an automatic-exchange jurisdiction, which places American-source income in the lowest category — genuinely good news for our readers, and a point almost every generic WDF article omits because it is written for taxpayers with money in traditional secrecy jurisdictions.
Failure to Correct: the penalty floor most people miss
Sitting underneath the ordinary offshore penalties is a harsher regime for historic years. Taxpayers were required to correct any offshore non-compliance relating to periods before 6 April 2016 by 30 September 2018. Anyone who did not now falls within the Failure to Correct rules for those years.
Under FTC the standard penalty is 200% of the tax, reducible to 150% for a prompted disclosure that is full and accurate, and to a floor of 100% for an unprompted one. That floor is the critical number: however cooperative you are, the minimum penalty on a pre-April-2016 FTC year is 100% of the tax — you pay the tax twice.
Additional sanctions can apply in the most serious cases, including an asset-based penalty of up to 10% of the value of the asset connected to the failure, and public naming. Those are reserved for deliberate behaviour above materiality thresholds, but they exist and they change the calculus of leaving a disclosure unmade.
Interest, and why it now dominates older years
Interest runs on the unpaid tax from each year's original due date. It is not a penalty, so there is no reasonable excuse defence and no mitigation for cooperation — it simply accrues.
HMRC's late payment interest rate has been 7.75% since 9 January 2026, set in legislation at the Bank of England base rate plus four percentage points. On a twelve-year disclosure, interest on the earliest years can approach or exceed the tax itself, and it is calculated year by year at the rates then prevailing rather than at one flat rate.
This is why delay is expensive even in a case where the penalty is agreed at the minimum. Every month spent deciding whether to disclose adds interest to twelve years of balances at once.
Prompted versus unprompted is worth real money
A disclosure is unprompted only if you had no reason to believe HMRC had discovered, or was about to discover, the non-compliance. Once a nudge letter arrives, or a compliance check opens, any disclosure is prompted.
The difference is not cosmetic. Under Failure to Correct, unprompted takes the penalty to the 100% floor while prompted stops at 150%. Under the ordinary offshore penalties, the reduction ranges for unprompted disclosures are materially wider at every behaviour level.
So the value of acting before the letter arrives, on a £60,000 pre-2016 liability, is roughly £30,000. That is the actual price of waiting to see whether HMRC notices.
How the WDF differs from the IRS programmes
Americans who have already been through a US catch-up frequently assume HMRC works the same way. It does not, and the differences run in the direction that catches people out.
The IRS Streamlined Foreign Offshore Procedures carry a 0% penalty for a taxpayer who certifies non-willful conduct — a genuine amnesty. The WDF has no equivalent. There is no certification of innocence that switches penalties off, no fixed programme penalty, and no assurance against criminal investigation. HMRC's protected route for taxpayers who fear prosecution is a different mechanism entirely, the Contractual Disclosure Facility under Code of Practice 9.
The second difference is scope. Streamlined is three years of returns and six of FBARs, fixed. The WDF is however many years your behaviour dictates, which can be four or twenty. Our comparison of quiet disclosure versus the streamlined route sets out the American side of the same decision.
Sequencing a two-country catch-up
Most people in this position have a gap on both sides: undeclared US-source income in the UK, and unfiled or incomplete US returns. Fixing them in the wrong order creates two inconsistent records of the same money.
The dependency runs in one direction. The UK disclosure needs to know what UK tax is due after foreign tax credit relief for US tax actually paid, and the US returns need to know what UK tax was paid to compute the American credit. Where both are being restated, settle the underlying income figures once, then compute both countries from the same reconstructed dataset.
In practice that means one reconstruction exercise, two sets of computations and two submissions timed so that neither contradicts the other. Where a US catch-up is also needed, our guides to how many years of US returns you must file and the Form 14653 non-willfulness statement cover that half.
A worked example
An American who moved to London in 2011 declared her UK salary every year but never declared a US brokerage account, which generated around £9,000 a year of dividends and periodic realised gains. She was careless rather than deliberate: she genuinely believed US-source income was taxed only in America, and no adviser told her otherwise.
Careless behaviour on an offshore matter gives HMRC a twelve-year window, so the disclosure covers 2014/15 onwards. Years from 2016/17 fall under the ordinary offshore penalty regime, where the United States is a category 1 territory and cooperative unprompted disclosure can reduce the penalty substantially. The pre-6 April 2016 years fall under Failure to Correct, where the floor is 100% of the tax however helpful she is.
Foreign tax credits for the US tax she actually paid on the same dividends reduce the UK tax materially — but they reduce the tax, and the penalty is a percentage of the tax, so the credits reduce the penalty too. That is the one piece of leverage in the whole calculation, and it is why the credit position should be computed properly before any penalty is self-assessed. You can size the separate UK late filing exposure with our UK Self Assessment penalty calculator.
What to do now
Establish three things before you touch the Digital Disclosure Service: which years are actually in scope, whether any of them fall before 6 April 2016, and what your behaviour category honestly is. Those three answers determine the entire cost, and none of them improves by being decided quickly.
Then reconstruct the numbers, compute the foreign tax credit relief, and only then notify — so that the 90-day clock runs against work that is already largely done. If a nudge letter has already arrived, invert that order and request the complex-case extension at notification.
TaxStone prepares Worldwide Disclosure Facility submissions for Americans in the UK alongside the US filings that usually need correcting at the same time, so the two countries are reconciled once rather than argued about twice. If you have undeclared offshore income or a letter you have not answered, contact us with the years involved and we will scope it before anything is notified.
