Missed UK Tax Returns: US Spin-Off Shares for UK Residents

A US spin-off that is tax-free under section 355 is not automatically tax-free in the UK. For a UK-resident American, the new shares may be taxed as foreign dividend income, as a capital distribution, or as a no-disposal reorganisation. If nothing reached the Self Assessment return, the missed years can usually be put right through a structured disclosure.

Most UK-resident Americans who hold a large US-listed portfolio know the new shares arrived tax-free on their US return. Very few realise that HMRC asks a different question. Missed UK tax returns caused by a spin-off are among the most common gaps we find when we review the UK filings of US citizens who have lived in Britain for years. Brokers issue no UK paperwork. The US issuer's tax notice talks only about US basis. The sterling value of the shares distributed can easily run into six figures. This guide explains how HMRC approaches a US spin-off, how to work out the UK base cost of the old and new shares, what belongs on the foreign pages of the return, and how to correct earlier years without making the position worse.

Why a US "tax-free" spin-off can be taxable in the UK

In the United States, section 355 of the Internal Revenue Code lets a corporation distribute the stock of a controlled subsidiary to its shareholders without recognising gain at either level, provided the statutory tests are met (control, active trade or business, business purpose and the anti-device rule). The shareholder simply splits their existing basis between the old and new stock. Nothing is reported as income.

The UK has its own demerger code, but it was written for UK companies. The exempt distribution rules in Part 23 Chapter 5 of the Corporation Tax Act 2010 remove what would otherwise be a taxable distribution, and section 192 of the Taxation of Chargeable Gains Act 1992 then treats the demerger as a reorganisation for capital gains tax. Those rules depend on conditions that a US corporation distributing US subsidiary shares will not normally meet, because they are framed around a UK-resident distributing company. A US spin-off therefore falls back on the general rules, and under those rules the default risk is income.

The income charge on foreign distributions

UK residents pay income tax on dividends from non-UK resident companies under the Income Tax (Trading and Other Income) Act 2005. The charge excludes "dividends of a capital nature", but that exclusion is narrower than most people assume. In Beard v HMRC [2025] EWCA Civ 385, the Court of Appeal confirmed that the character of a foreign distribution turns on the company-law mechanism the foreign company used to make it. Paying a distribution out of a capital-type reserve does not, by itself, make it capital. A distribution made through the ordinary dividend machinery of the company's corporate law is likely to be income, whatever the source of the funds.

That matters because many US spin-offs are carried out by the parent's board declaring a dividend of the subsidiary's shares under state corporate law. Unless the facts support a different analysis, HMRC can argue that the market value of the shares received is foreign dividend income in the tax year of the distribution, taxed at dividend rates. From 6 April 2026 those rates are 10.75%, 35.75% and 39.35%, with only a £500 dividend allowance.

Three possible UK outcomes

In practice, the UK analysis of a US spin-off lands in one of three places:

• Income distribution: the market value of the new shares is foreign dividend income. That value then becomes the base cost of the new shares, and the base cost of the original shares is unchanged.
• Capital distribution (section 122 TCGA 1992): the new shares are treated as a capital receipt from the original holding. That is a part disposal of the original shares, unless the distribution is "small" compared with the value of the holding. HMRC practice treats a distribution of 5% or less, or of £3,000 or less, as small.
• Reorganisation treatment: there is no disposal. The new shares are treated as acquired when the original shares were acquired, and the original base cost is apportioned between the two lines.

Which outcome applies depends on the legal form of the transaction, the corporate law governing the parent and, for many large transactions, the view HMRC has already taken of that particular demerger.

How relevant is HMRC's treatment of specific foreign demergers?

For widely held US spin-offs, HMRC has in the past given its view on particular transactions. Some issuers with significant UK shareholder bases also publish UK tax information, or obtain and share HMRC's confirmation of the treatment. Where such a view exists, it is the natural starting point for your return. HMRC is unlikely to take a different position from the one it has published or confirmed for the same transaction, and a filing that follows it is easy to defend.

Where no such view exists, the position has to be analysed from first principles, including the parent's corporate law, how the distribution was declared and accounted for, and whether the transaction is closer to a reconstruction than a dividend. Documenting that analysis properly is part of the filing. If a disclosure is later questioned, an "insufficiently considered" position is treated very differently from one supported by a reasoned note.

This area is also under review. HMRC's 2026 consultation, Modernising the taxation of distributions and repayments of capital from companies, looks at both the demerger rules and the income tax treatment of distributions from non-UK resident companies. It closed on 14 September 2026. It changes nothing for past years, but it confirms that the treatment of foreign distributions is a live policy issue and not a settled technicality.

Base-cost apportionment between old and new shares

Base cost is where the UK and US positions most visibly diverge, and where errors spread into later years. If reorganisation or capital distribution treatment applies, the original sterling base cost has to be split between the parent shares and the spin-off shares. For quoted shares, the reorganisation rules in sections 129 and 130 TCGA 1992 generally apportion cost by reference to relative market values on the first day of dealing after the reorganisation (see HMRC's Capital Gains Manual at CG51890). The issuer's US basis percentages usually rest on a similar valuation principle, but they are not binding for UK purposes, and the UK calculation must be run in sterling.

Three technical points are often missed:

• Sterling, not dollars. UK base cost is the sterling cost of each acquisition, converted at the rate on the acquisition date. Apportioning a US-dollar basis and then converting it at today's rate gives the wrong answer.
• Share pooling. The original holding will usually be a section 104 pool built from many purchases, dividend reinvestments and vested awards. Under reorganisation treatment, the new line inherits a proportion of that pool. Under income treatment, it starts a new pool at market value.
• Employment-related shares. Executives often hold parent stock from RSUs or options. An adjustment to unvested awards may fall under employment-related securities rules rather than capital gains rules, and should be looked at separately.

Worked example

Consider a UK-resident US citizen who holds 10,000 parent shares with a sterling base cost of £640,000. The parent distributes one spin-off share for every four held, so 2,500 new shares arrive. On the first day of dealing, the parent trades at $120 and the spin-off at $60, giving values of $1,200,000 and $150,000. The spin-off therefore represents about 11.1% of the combined value. Assume an exchange rate of $1.30 to the pound on the distribution date.

UK treatment	What is taxed in the year of the spin-off	Base cost of spin-off shares	Base cost of parent shares
Income distribution	About £115,385 of foreign dividend income (worth roughly £45,400 of tax at the 39.35% additional rate)	£115,385 (market value)	£640,000 (unchanged)
Capital distribution (not small)	Part disposal: proceeds £115,385 less apportioned cost of about £71,111, a gain of about £44,274 before the annual exempt amount	About £71,111	About £568,889
Reorganisation	Nothing	About £71,111	About £568,889

The spread between the three outcomes is large, which is why the classification has to be settled before any figure goes on a return. It also shows why ignoring the spin-off is never neutral. Even where reorganisation treatment applies and no tax was due that year, the base cost of both lines has changed, and every later disposal computed on the old figure will be wrong.

What goes on the Self Assessment return

For a UK-resident American, the spin-off is reported on the supplementary pages that go with the main SA100:

• Foreign pages (SA106): if the distribution is income, its sterling value goes in as a dividend from a foreign company. US withholding is usually nil on a section 355 distribution, so normally there is no foreign tax credit to claim for that year. See HMRC's SA106 foreign pages and notes.
• Capital gains pages (SA108): if the distribution is a non-small capital distribution, the part disposal goes here. Later sales of either the parent or spin-off shares, and any cash in lieu of fractional shares, also go here.
• Additional information (white space): where the treatment rests on a judgement, such as reliance on an HMRC view of a specific demerger or a reorganisation analysis, a short note of the position taken helps protect against a later discovery assessment.

Former non-domiciled individuals need an extra step. Before 6 April 2025, a US citizen who claimed the remittance basis was taxed on foreign income only when it was remitted, so an income-treated spin-off held offshore may not have been taxable in the year it arrived. After the remittance basis was abolished, long-term residents are taxed on the arising basis, and any claim to the four-year foreign income and gains regime has to be checked year by year. Your remittance history therefore shapes the correction.

The US side, briefly

If the transaction qualifies under section 355, a US shareholder recognises no income or gain on receiving the spin-off shares. Tax basis in the original shares is allocated between the old and new stock in proportion to their fair market values. The issuer publishes the allocation percentages on IRS Form 8937, Report of Organizational Actions Affecting Basis of Securities, and brokers normally adjust cost basis on that footing. The holding period of the new shares includes the holding period of the old shares.

Cash paid in lieu of a fractional share is the exception. It is normally treated as though the fractional share was received and then sold, producing a small capital gain or loss reported on Form 1099-B and Form 8949. The UK normally treats the same cash as a small disposal, or as a reduction in base cost where the amount is small.

For a US citizen living in the UK, the US return and the UK return therefore describe the same event in very different terms. Our US tax services team sees this regularly when reconciling a client's two sets of filings.

The timing mismatch that leaves UK tax uncreditable

This is the core cross-border problem, and it is where generalist advice usually stops. If HMRC treats the spin-off as income, the UK charges tax in year one. The US charges nothing in year one, because section 355 applies. There is no US tax on that income for the UK to credit, and no US income in that year against which the UK tax could be credited on the US return.

Years later, when the shares are sold, the positions reverse. The UK taxes a smaller gain because the income charge has already stepped up the UK base cost of the spin-off shares. The US taxes a larger gain because the US basis was only a carved-out share of the original cost. Foreign tax credit rules match foreign taxes to income by category and year. The one-year carryback and ten-year carryforward, and the resourcing rules in the US-UK treaty, do not always bridge a gap that turns income in one country into a capital gain in the other, years apart. Part of the value of the UK tax paid on the spin-off can be permanently lost.

Issue	United States (IRS)	United Kingdom (HMRC)
Receipt of spin-off shares	Tax-free if section 355 is met	Income, capital distribution or reorganisation, depending on form and HMRC's view
Governing rules	IRC sections 355 and 358	ITTOIA 2005 (foreign dividends); TCGA 1992 sections 122 and 126 to 131
Basis or base cost	Allocated by fair market value per the issuer's Form 8937	Sterling cost, apportioned at market value, or a market-value cost if taxed as income
Cash for fractions	Deemed sale; capital gain or loss	Disposal, or a reduction in cost if small
Reporting	Form 1040; Form 8949 for cash in lieu and later sales	SA106 (if income) and SA108 (disposals)
Double-tax relief	Foreign tax credit limited by category and year	Credit for US tax only where US tax is actually charged on the same income

Because the credit mismatch cannot always be fixed after the event, the order in which the two returns are corrected matters. Where both countries' returns are open or being amended, the positions should be designed together, not handled by two advisers working in isolation. This is where a joint US-UK tax accountant earns their fee.

Correcting missed years with HMRC

Income and gains from US-listed shares are "offshore" matters for HMRC purposes. That brings longer assessment windows and higher penalty ranges than purely domestic errors. HMRC can generally go back 4 years for innocent errors, 6 years where the taxpayer was careless and 20 years for deliberate behaviour. For offshore income and gains, the careless-error window has been extended to 12 years. A spin-off from a decade ago can therefore still be in scope.

A practical correction sequence

• Establish the facts: record dates, ratios, first-day trading prices, cash in lieu and the issuer's Form 8937. Check whether HMRC has published or confirmed a view on that particular demerger.
• Classify the event: decide between income, capital distribution and reorganisation, and document the reasoning.
• Rebuild base costs in sterling: rebuild the section 104 pools for both lines, and recompute every later disposal of either line. Reorganisation cases often show that past gains were overstated as well as understated.
• Choose the route: use an amendment within the normal window, which runs to 12 months after the 31 January filing deadline for that year. For older years, use a disclosure through HMRC's Digital Disclosure Service, normally the Worldwide Disclosure Facility for offshore matters.
• Quantify tax, interest and penalties: an unprompted disclosure with full co-operation attracts the lowest penalties. A reasonable-care case, supported by the complexity of the treatment, can reduce them to nil.
• Align the US side: make sure US basis records match the Form 8937 allocation. If other US gaps come to light, such as unreported UK accounts on FBAR or Form 8938, consider whether the IRS Streamlined Filing Compliance Procedures should run alongside the HMRC disclosure.

Is a disclosure always needed?

Not always. If reorganisation treatment applies and neither line has been sold, there may be no tax to pay. The correction is then mainly a matter of fixing base-cost records before the next disposal. But if the shares were income-treated, or later disposals were computed on the wrong base cost, the tax may be understated, and waiting only lengthens the interest period. A precise review usually settles the question quickly.

Why this matters for high-net-worth portfolios

For clients with concentrated holdings, a single spin-off can put a six- or seven-figure sterling value in play. Large US groups spin off businesses frequently, so a long-standing portfolio may have been through several such events, each with its own UK treatment and each changing the base cost of what remains. Our high-net-worth practice routinely finds that a portfolio's UK base costs have drifted from reality over many years for exactly this reason. Correcting them often reduces future gains as well as exposing past income.

Jungle Tax focuses on the compliance itself: classifying each corporate action, rebuilding sterling cost records, preparing the amended or disclosed UK returns and keeping the US filings consistent. We do not sell structuring. We make sure that what you have already received is reported correctly on both sides of the Atlantic. More worked examples are in our cross-border guides.

Key takeaways

• A section 355 spin-off that is tax-free in the US can still be taxable income in the UK, because the UK exempt demerger rules are built for UK companies.
• Following Beard, the foreign company-law mechanism used for the distribution is central to whether it is income or capital.
• HMRC's published or confirmed view on a specific foreign demerger, where one exists, is the natural reference point.
• Sterling base cost must be apportioned between the old and new shares. It is not a copy of the Form 8937 percentages converted at today's rate.
• Income treatment in the UK with no US tax charged can leave UK tax permanently uncreditable. Coordinate both returns.
• Offshore time limits of up to 12 years for careless errors mean older spin-offs are still in scope. An unprompted disclosure gives the best penalty outcome.

If you have received spin-off shares from a US holding and are unsure whether your UK returns reflect them, we can review the position confidentially. We will classify each corporate action, rebuild your sterling base costs and, where needed, prepare the corrected returns or disclosure. Contact our cross-border team for a confidential consultation.