White Space Disclosure on Late UK Tax Returns: What to Write

White space disclosure is the free-text "Any other information" entry (box 19, page TR 7 of the SA100) where you explain how a return was prepared. On a late UK return it decides whether HMRC can reopen the year by discovery after the enquiry window closes, but only if a return exists and you were not careless or deliberate.

For an American who is bringing several years of UK Self Assessment up to date, usually alongside a US catch-up, the white space is not a formality. It is the one place on the return where you control what HMRC is treated as knowing. At Jungle Tax we draft it as carefully as the figures themselves, because a catch-up year is full of positions HMRC cannot see from the numbers alone: how a Delaware LLC has been characterised, which exchange rates were used, whether the foreign tax credit rests on US tax actually paid or on a draft Form 1040, and which figures are waiting for US returns that have not yet been filed.

This guide stays on the UK side. If you want the comparison with the US disclosure regime, it is in our guide to Form 8275 adequate disclosure on late-filed catch-up returns. We also do not cover discovery assessment time limits here. What follows is the UK mechanism, the late-return enquiry window, and what to actually write for each US-connected position.

What is white space disclosure, and where does it sit on the return?

The SA100 main return has an "Any other information" space at box 19 on page TR 7. HMRC's own notes say it may be used for details of any estimates or provisional figures you have used, and they point out that figures entered there are not included in your tax calculation. Anything that affects the tax must still go in the correct box elsewhere on the return. The white space explains the numbers; it does not replace them.

Box 20, directly below it, is the provisional-figures box. HMRC's notes are specific:

• Put "X" in box 20 only if you have used provisional figures and intend to send final figures as soon as you can.
• If you tick it, you must say in box 19 why you have used provisional amounts and when you expect to give HMRC the final figures.
• If you have used estimated figures, meaning figures you do not expect to revise, do not tick box 20, but still explain in box 19 why you have estimated.

That distinction matters a great deal in a US-UK catch-up, and we come back to it below. The notes for the current return are on the SA100 publication page on GOV.UK.

Can you attach a schedule instead?

Often you should. HMRC's Self Assessment Manual confirms that returns filed online can carry PDF attachments of additional information (see SAM126040). HMRC's own online service limits how many attachments you can send; commercial software may allow more, but a total file-size cap still applies. Every attachment is virus-checked, and HMRC warns that a valid return may be rejected if an attachment is rejected. After filing, confirm the return was accepted and keep the submission receipt.

Documents accompanying the return count as information made available for discovery purposes, so a properly attached computation schedule is protective. Our practice is to write a self-contained summary in box 19 that names each attached schedule. The box then works on its own, and the schedule supplies the arithmetic.

How does white space disclosure limit HMRC's power to reopen a year?

The mechanism is section 29 of the Taxes Management Act 1970. Where an officer discovers that tax has been under-assessed, they can make a discovery assessment. But where the taxpayer has delivered a Self Assessment return for the year, section 29(3) blocks the assessment unless one of two conditions is met:

• The first condition (section 29(4)). The under-assessment was brought about carelessly or deliberately by the taxpayer or someone acting on their behalf.
• The second condition (section 29(5)). At the time HMRC ceased to be entitled to open an enquiry into the return, or completed an enquiry into it, an officer could not have been reasonably expected, on the basis of the information made available before then, to be aware of the under-assessment.

White space disclosure works on the second condition only. The full text is on legislation.gov.uk, and HMRC's own reading is in Enquiry Manual EM3233.

What counts as "information made available"?

Section 29(6) sets out a closed list:

• information in the return for the year, and in any accounts, statements or documents accompanying it;
• information in any claim made for the year, and documents accompanying it;
• documents, accounts or particulars produced, or information provided, for the purposes of an enquiry into the return or claim;
• information whose existence, and relevance to the under-assessment, an officer could reasonably be expected to infer from the above, or which the taxpayer has notified in writing to an officer.

Section 29(7) extends "the return" to the returns for the two immediately preceding years. In a batch catch-up that is useful: a clear note in the 2021-22 return about how a Delaware LLC has been characterised is also information made available for the 2022-23 and 2023-24 returns. We still repeat the disclosure in every year, because each return is judged on its own, and a note that relies on an earlier year invites argument about whether the inference was reasonable.

What is missing from the list matters as much. Data HMRC receives from overseas tax authorities under automatic exchange, figures on your US returns, and anything held on third-party systems are not in the statutory list. HMRC may well hold details of your US accounts, but unless that information is in your return, a document accompanying it, a claim, enquiry material, or a written notification from you, it does not help you under section 29(5).

The hypothetical officer and the "actual insufficiency" test

The officer in section 29(5) is not the real inspector on your file. Appellate courts have described a hypothetical officer of general competence, knowledge and skill, with a reasonable understanding of the law, but not a specialist in US entity classification or offshore funds. Three lines of case law set the bar:

• Awareness, not curiosity. The Court of Appeal has held, first in 2004 and again in 2016, that it is not enough for the return to prompt the officer to ask questions. The information must make the officer aware of an actual under-assessment, clearly enough to justify raising an assessment.
• Full, clear disclosure can win. In 2012 the Upper Tribunal upheld a disclosure that described the arrangements plainly enough that no competent officer could have missed what had been done. The point was not length. The note said exactly what the taxpayer had done and how it had been treated.
• The bar has risen. A 2021 Upper Tribunal decision set the standard high enough that, in practice, only full and specific disclosure is a reliable defence. A 2022 First-tier Tribunal decision found the taxpayers' agent careless despite a white space note, so the first condition applied and the note did not help.

The same year, the Supreme Court held that a "deliberate" inaccuracy requires an intention to mislead HMRC. A return that openly explains an unusual entry is not deliberately inaccurate just because the entry sits in the wrong box. The Court also rejected the idea that a discovery goes "stale" if HMRC waits to act on it. The practical lesson for a catch-up is that the explanation you give on the return is evidence of what you intended.

HMRC's own statement on what to disclose

HMRC's Statement of Practice 1/2006 remains the most useful official guide to drafting. It encourages taxpayers to provide the minimum necessary to disclose an under-assessment, and warns that a pile of unhighlighted material may not count as information made available. Where a valuation has been used, saying so, identifying the valuer, and confirming they were independent and suitably qualified will normally give protection, provided those statements are true. Where a taxpayer takes a different view of the law from HMRC's published guidance, the Statement expects the return to say so, and finality then follows if no enquiry is opened within the statutory window. Section 29(2) separately protects a return made on the basis of practice generally prevailing when it was filed.

What white space disclosure cannot do

Clients sometimes treat the white space as a safe harbour. It is not one, and in a catch-up there are three limits to understand before drafting.

It does not help if the behaviour was careless or deliberate

If HMRC can show that the under-assessment was brought about carelessly, the first condition is met and the quality of the note is irrelevant to whether a discovery assessment can be made. Deliberate behaviour is worse still. A note cannot clean up a position that was not supportable when adopted. What it can do is evidence reasonable care. A note that shows the question was identified, analysed, and resolved on a stated basis is strong evidence against carelessness. A note that simply says "treatment uncertain" is not.

It does not help a year for which no return was delivered

The section 29(3) protection only exists where a return has been delivered. HMRC's manual states plainly that neither condition applies where no return was made or in failure-to-notify cases. So a year that is never filed, or that is brought into account through a disclosure facility rather than a Self Assessment return, has no return for the white space to protect. Finality for those years comes from how the disclosure is settled. That is one reason we look closely at which route each year should take when a UK disclosure runs alongside an IRS streamlined submission.

Check, too, that the return you are filing is actually a return under section 8. A section 8 return is made in response to a notice to file. If the old years were never covered by a notice, ask HMRC to issue one before you file, rather than sending what may turn out to be an unsolicited document.

It invites scrutiny inside the window

A well-drafted note tells HMRC exactly where the interesting question is. That is intentional. For a wealthy catch-up filer, an enquiry inside the window is usually far better than a discovery assessment years later, because an enquiry is the procedure in which the position gets tested and then closed. Disclosure trades the chance that nobody looks for the certainty that, once the window closes without an enquiry, the disclosed position is settled.

How long is the enquiry window on a late return?

The section 29(5) test is applied at the moment HMRC stops being entitled to open an enquiry. For a late return, you need to know exactly when that is. Section 9A(2) gives the rule:

• Return delivered on or before the filing date: the window runs to the end of twelve months after the day the return was delivered.
• Return delivered after the filing date: the window runs up to and including the quarter day following the first anniversary of delivery. The quarter days are 31 January, 30 April, 31 July and 31 October.
• Return amended: the window runs to the quarter day following the first anniversary of the amendment.

Worked example. A US citizen resident in London files her 2022-23 return on 10 September 2026. The filing date was 31 January 2024, so the return is late. The first anniversary of delivery is 10 September 2027, and the next quarter day is 31 October 2027. HMRC can open an enquiry up to and including 31 October 2027. From then on, whether the year can be reopened by discovery depends on what her return, its attachments, and any written notifications delivered before that date told a hypothetical officer.

The filing date itself is not always 31 January. Under section 8, where HMRC gives the notice to file after 31 October following the tax year, the return is due within three months beginning with the date of the notice. An old year for which HMRC issues a notice today is not late if you file within those three months. In that case the twelve-month rule applies instead of the quarter-day rule, and late-filing penalties do not arise for that year. Establish the notice date for each year before you plan the batch.

Two practical consequences follow. First, because the window runs from delivery, filing six years on the same day gives six windows that close together, which simplifies monitoring. Second, anything you notify in writing to put the record straight, such as final figures replacing provisional ones, only counts under section 29(5) if it reaches HMRC before the relevant window closes.

What should a white space note actually say?

The case law points to a consistent structure. For every position that the figures alone would not reveal, the note should state:

1. The facts. What the asset, entity or income is, in plain terms, with names and dates.
2. The treatment adopted. How it has been taxed on this return, and where on the return it appears.
3. The amounts. The sterling figures involved, so an officer can quantify the point without asking.
4. The basis. The documents relied on and, where the treatment departs from HMRC's published view, a clear statement that it does so and why.
5. Anything provisional. Which figures will change, why, and when final figures will follow.

The test we apply internally is simple: could an officer of general competence, reading only this return and its attachments, raise an assessment for the alternative treatment without writing to us first? If not, the note is not finished.

What to write for US-connected positions in a catch-up return

These are the positions that come up in almost every American catch-up we prepare. None of them can be seen from the boxes alone, and each has a failure mode that generic white space advice does not address.

Treaty positions

Identify the article relied on, the facts that engage it, and where the claim appears on the return. For a dual-resident year, give the tie-breaker analysis under Article 4 in summary: permanent home, centre of vital interests, habitual abode. Where employment income relates to US workdays, state the day count, how it was established, and whether the income is taxed in the UK with credit or relieved in some other way. State the treaty position only once, clearly, and cross-refer to it in later years rather than rewording it.

US LLC characterisation

This is the position most likely to be reopened. HMRC's International Manual has, since June 1997, listed US LLCs as opaque, meaning companies for UK purposes (INTM180030). A 2015 Supreme Court judgment allowed double tax relief to a UK-resident member of a Delaware LLC on the basis that he was entitled to his share of the profits as they arose. HMRC's published response in September 2015 treated the decision as specific to its facts and said that claims relying on it would be considered case by case. HMRC refreshed its entity-classification guidance in December 2023 without changing that default.

If the return treats the LLC as opaque, say so and state that distributions received are reported as foreign dividends, with the amounts. If it adopts transparent treatment, the note must say that this departs from HMRC's general view, identify the LLC and its state of formation, summarise the operating-agreement terms relied on (how profits are allocated, whether members are entitled to them as earned), and give the sterling profit share included. A transparent position without that statement is exactly what Statement of Practice 1/2006 asks taxpayers to flag. Our guide to US LLC ownership for UK residents covers the substantive analysis.

S corporation shares

The US taxes an S corporation shareholder on their share of the company's profits whether or not anything is distributed. The UK generally treats an S corporation as a company and taxes the shareholder on distributions. The note should state that the shareholding is reported as an interest in a foreign company, list the distributions received and the dates, confirm that undistributed profits shown on the Schedule K-1 are not included as UK income, and explain how any US tax has or has not been credited against the UK tax on those distributions. The timing mismatch is explored in our note on S corporation shareholders resident in the UK.

Exchange-rate method

HMRC's Capital Gains Manual expects white space disclosure where currency computations cannot be done strictly because information is missing, setting out the basis on which the figures were prepared (CG78409). For a US-connected return, name the rate source (HMRC's published monthly or yearly average rates, or daily spot rates) and state that it is used consistently. For capital gains, confirm that the dollar cost and the dollar proceeds were each converted to sterling at the rate on their own dates. A gain computed in dollars and converted once is a different number, and the difference is an under-assessment an officer could not see without being told.

Foreign tax credit relief computed on US tax paid or estimated

HMRC's helpsheet on relief for foreign tax paid invites taxpayers to use the white space on page TR 7 to explain the ordering and calculations behind a credit claim (HS263). For a US citizen, the note should also deal with the treaty restriction. Under Article 24 of the US-UK treaty, the UK credits US tax on a UK-resident US citizen only up to the amount the US could charge a UK resident who is not a US citizen. In practice that means 15% on portfolio US dividends, and usually nil on US-source interest and on most capital gains, which the treaty leaves to the country of residence. The US then gives its own credit for the UK tax. A UK return that credits the full US tax is over-claiming, and the note is where you show the officer that the cap has been applied.

State whether the US tax figure comes from a filed Form 1040 or a draft, how the calendar-year US tax has been apportioned to the UK tax year, and the exchange rate used to convert it. If the US return is not yet filed, the credit is provisional (see below). A credit claim has its own time limit under section 19 of the Taxation (International and Other Provisions) Act 2010: the fourth anniversary of the end of the tax year or, if later, 31 January following the tax year in which the foreign tax is paid. That gives some flexibility where US tax is paid late in a catch-up. If the US liability later falls, the credit must be revisited and HMRC told.

Provisional figures awaiting US returns

The honest position in a joint catch-up is often that the UK return is ready before the US returns are finalised. Do not hold back the UK return. Enter your best figures, put "X" in box 20, and in box 19 say which figures are provisional (typically the foreign tax credit and any K-1 income), why (the US federal return for the corresponding calendar years is being prepared as part of a concurrent catch-up), and when you expect to supply final figures. HMRC's notes warn that a penalty can follow where provisional figures are used without good reason or are unreasonable, so the figures must be a genuine best estimate.

Plan how the final figures will reach HMRC. A section 9ZA amendment is only possible within twelve months of the filing date, which for a year filed years late has usually already passed. The usual route is a written notification of the final figures, sent before the quarter-day enquiry deadline, which then counts as information made available.

Reliance on US information returns

Most US-source figures on a catch-up return come from Forms W-2, 1099-DIV, 1099-INT, 1099-B and Schedules K-1. Say so, because those documents cover the US calendar year and the UK tax year runs from 6 April to 5 April. The note should explain how calendar-year documents were converted to UK tax-year figures: payment dates from broker statements, apportionment by months, or transaction-level data. It should also cover the traps in these forms:

• Nondividend distributions. Amounts reported on a 1099-DIV as return of capital. State whether they reduce base cost or are taxed as income.
• US funds. Many US-domiciled mutual funds and exchange-traded funds do not hold UK reporting fund status. Gains on non-reporting funds are taxed as income, not capital gains. State that reporting status was checked against HMRC's published list for the relevant periods, and where any offshore income gain has been entered.
• Corrected or late forms. If a corrected 1099 or a late K-1 is expected, say which figures depend on it.
• Wash-sale and basis adjustments. These are US concepts. State that UK gains have been computed under UK share-matching rules from transaction data, not taken from the 1099-B gain column.

US and UK treatment of the same item: what the note must bridge

The white space is most valuable where the US and UK treat the same item differently, because an officer reading a UK return has no reason to expect the difference. The table below sets out the recurring mismatches and what the note needs to record.

Item	US treatment	UK treatment on the return	What the note must record
Single-member US LLC	Usually disregarded; profits taxed directly on the owner's return	Opaque company in HMRC's general view; transparent treatment only on specific facts	Treatment adopted, operating-agreement facts, sterling amounts, any departure from HMRC's published view
S corporation	Pass-through; shareholder taxed on share of profits via K-1	Generally a company; shareholder taxed on distributions	Distributions and dates, confirmation that undistributed profits are excluded, credit basis
US-domiciled funds and ETFs	Capital gain or qualified dividend treatment	Often a non-reporting offshore fund; disposal gain taxed as income	Reporting status checked, periods covered, where the gain is entered
Dividends and interest	Calendar-year Forms 1099	Taxed by UK tax year, 6 April to 5 April	Apportionment method and source documents
US tax credit	US credits UK tax after treaty re-sourcing	UK credits US tax only up to the non-citizen treaty amount	Rates applied, filed or draft US figures, conversion rate, provisional status
Currency	US dollar reporting	Sterling; cost and proceeds converted at date-specific rates	Rate source, method, consistency across years

An illustrative note for a catch-up year

This is a structural example for a 2022-23 return filed late, not wording to copy without advice on your own facts:

1. This return is delivered late as part of a voluntary catch-up of the 2019-20 to 2024-25 returns. The taxpayer is a US citizen resident in the UK throughout. US federal returns for calendar years 2022 and 2023 are being prepared concurrently.

2. Currency: US dollar income is converted at HMRC's published average rate for the year to 31 March 2023. Capital gains are computed by converting cost and proceeds separately at the daily rate on each date. See attached schedule A.

3. US brokerage income: dividends and interest are taken from the 2022 and 2023 Forms 1099 and allocated to the UK tax year by payment date from monthly statements. Return-of-capital distributions of £[x] reduce base cost. Schedule B.

4. Funds: [fund names] are not on HMRC's list of reporting funds for the periods held. The gain of £[x] on disposal of [fund] is included as an offshore income gain.

5. [Name] LLC (Delaware, single member, disregarded for US purposes) is treated as opaque. Distributions of £[x] are included as foreign dividends. No UK income is returned for undistributed LLC profits.

6. Foreign tax credit: US tax is taken from draft Forms 1040, apportioned to the UK tax year by [method], and limited under Article 24 of the US-UK treaty to the tax chargeable on a non-US-citizen UK resident (15% on US dividends; nil on US interest and gains). These figures are provisional (box 20). Final figures will be notified in writing by [date], once the US returns are filed. Schedule C.

Each numbered point gives the facts, the treatment, the amount and the basis. None of them relies on HMRC making inquiries to understand it.

Common drafting mistakes on catch-up returns

• Vague notes. "Some figures may require adjustment" tells an officer nothing and protects nothing. The case law needs awareness of an actual under-assessment.
• Document dumps. Attaching a full US return set without explaining what matters. Statement of Practice 1/2006 warns that unhighlighted material may not count.
• Ticking box 20 without a plan. Final figures that never arrive, or arrive after the enquiry window, leave the year exposed.
• Inconsistency across years. An LLC treated as opaque in one year and transparent in the next, with no explanation, points an officer straight to carelessness.
• Contradicting the US narrative. The UK note and any US disclosure or streamlined narrative must describe the same facts in the same way.
• Relying on data HMRC already holds. Exchanged account data is not information you made available.

Does white space disclosure reduce penalties as well?

Indirectly. Inaccuracy penalties turn on behaviour, and a clear contemporaneous note is good evidence that reasonable care was taken. Where an inaccuracy is found, a note that already identified the point supports treating the disclosure as unprompted and helps with mitigation. It does not remove late-filing penalties, which are a separate regime. It also cannot rescue a position the tribunal considers careless to have adopted. The US side of the penalty picture, and how the two regimes compare, is covered in the Form 8275 guide rather than repeated here.

For clients filing both countries' returns together, the sequence matters: the UK white space, the US disclosures and any IRS streamlined filing narrative are drafted from one set of facts, by one team, so that nothing said on one side of the Atlantic undermines the other. That is the core of our US-UK tax accountants practice.

Speak to us before the batch is filed

The white space is written once, at filing, and cannot be improved after the enquiry window closes. If you are an American bringing UK returns up to date, particularly with a US LLC, S corporation shares, US funds or a foreign tax credit that depends on US returns not yet filed, we will review each position, draft the disclosure to the standard the tribunals now expect, and map the enquiry deadline for every year. To arrange a confidential consultation, contact our cross-border team. We handle every catch-up discreetly, and nothing is filed until you are satisfied it is right.