Introduction: What Section 6501(c)(8) Does to a Tax Year You Thought Was Closed
Section 6501(c)(8) is the quietest and most dangerous provision in the Internal Revenue Code for an American living in Britain. Most people know that the Internal Revenue Service ordinarily has three years to assess additional tax, a rule set out in section 6501(a). Consequently they assume that a return filed in 2015 is beyond reach in 2026. That assumption is frequently wrong, and the reason is a single subsection that almost nobody reads.
Section 6501(c)(8) provides that where information required under one of nine listed provisions has not been furnished, the time for assessment "shall not expire before the date which is 3 years after the date on which the Secretary is furnished the information". Read that literally, because the drafting is deliberate. The clock does not run slowly. It does not run at all. Therefore a year in which you omitted a single foreign form remains open indefinitely — not for three years, not for six, but forever, until the form is actually filed. At TaxYork we routinely meet people whose 2012 returns are still legally open in 2026, and who had no idea.
Why Section 6501(c)(8) Exists
Congress had a practical problem. Offshore arrangements are difficult to detect, and the ordinary three-year window frequently expired before the Internal Revenue Service knew a foreign company or account existed. Accordingly, Section 6501(c)(8) ties the running of the assessment period to the receipt of information rather than to the filing of the return. In effect, the taxpayer holds the key: the clock starts when you hand over the disclosure, and not a day sooner. Whilst the logic is sound, the consequence for an ordinary compliant American in Britain who simply never knew about a form is severe.
The Nine Provisions That Trigger Section 6501(c)(8)
The subsection lists nine cross-references, and each corresponds to forms that Americans in Britain file constantly. Section 6038 covers Form 5471 for foreign corporations and Form 8865 for foreign partnerships, along with Form 8858 for foreign disregarded entities. Section 6046 also catches Form 5471, whilst section 6046A catches Form 8865. Section 6038A covers Form 5472, and section 6038B covers Form 926 on transfers of property to a foreign corporation. Section 6038D covers Form 8938 for specified foreign financial assets. Sections 1295(b) and 1298(f) cover Form 8621 for passive foreign investment companies, which in practice means most British investment funds. Finally, section 6048 covers Forms 3520 and 3520-A.
Notice what that list of Section 6501(c)(8) triggers means in practical terms. If you own a British limited company, hold a stocks and shares account containing UK-domiciled funds, or moved assets into a company at any point, you almost certainly have at least one form in this list. Moreover, the trigger is failure to furnish the information, not failure to owe tax. Therefore Section 6501(c)(8) bites just as hard on a year in which your liability was nil.
Section 6501(c)(8)(B): The Reasonable Cause Limit Almost Nobody Claims
Here is the provision that changes the outcome, and which the pages currently ranking for this topic mention in a single sentence, if at all. Subparagraph (B) states that if the failure to furnish the information "is due to reasonable cause and not willful neglect, subparagraph (A) shall apply only to the item or items related to such failure."
The distinction is enormous. Without reasonable cause, Section 6501(c)(8) holds open your entire return. With reasonable cause, it holds open only the items connected to the missing form. Everything else on that return — your employment income, your property gains, your foreign tax credit computations — falls back behind the ordinary three-year wall of section 6501(a) and becomes unassessable.
Consequently, reasonable cause under Section 6501(c)(8)(B) is not merely a penalty argument. It is a statute of limitations argument, and it is frequently worth far more than the penalty relief that taxpayers usually focus on. For an American in Britain who relied in good faith on a British accountant who never mentioned American filing obligations, the argument is often genuinely strong. Nevertheless, it must be documented contemporaneously and asserted properly, because the Internal Revenue Service does not apply subparagraph (B) on your behalf.
Section 6501(c)(8) Applies to the Whole Return, Not Just the Foreign Item
This point deserves its own emphasis because it is so widely misunderstood. In the absence of reasonable cause, the extended period reaches "any tax imposed by this title with respect to any tax return, event, or period to which such information relates". Courts and the Internal Revenue Service read that as the entire return, which is why Section 6501(c)(8) is so much more damaging than its placement in the Code suggests.
Therefore a missing Form 5471 for a dormant British company does not merely expose the company's profits. It exposes a share disposal you reported eight years ago, an employment bonus you sourced incorrectly, and a foreign tax credit basket you allocated wrongly. In short, one overlooked form converts an entire year of your financial life into an open assessment. Where several years are affected, as they usually are, the exposure compounds across all of them at once. Our note on amending a wrong US expat return explains how the corrective filing interacts with these windows.
How Section 6501(c)(8) Differs From the FBAR Statute
Confusion between the two regimes causes real harm, so it is worth separating them cleanly. The foreign bank account report is not filed under the Internal Revenue Code at all. It is filed with FinCEN under Title 31, and it carries its own six-year assessment window that runs from the filing due date regardless of whether you filed. Accordingly, that window does close, and it closes on schedule.
By contrast, Section 6501(c)(8) governs income tax assessment under Title 26 and never closes until the information arrives. As a result, an American in Britain can reach a point where the foreign account report years have expired whilst the income tax years remain wide open, or the reverse. Our detailed piece on the FBAR statute of limitations sets out the Title 31 side, and our article on Notice CP15 and FBAR penalty assessment covers what happens when a penalty is actually proposed.
The Six-Year Rule in Section 6501(e) Sits Alongside Section 6501(c)(8)
There is a further layer that compounds the position. Section 6501(e)(1)(A)(ii) extends the ordinary period to six years where the omitted gross income exceeds $5,000 and is attributable to an asset reportable under section 6038D. That is a low threshold, and it operates independently.
In practice, therefore, three separate clocks may be running on the same return simultaneously: the three-year rule, the six-year foreign asset rule, and the open-ended rule in Section 6501(c)(8). The longest one governs. Furthermore, none of these is affected by the fact that you filed honestly and paid what you believed was due. Good faith is relevant to reasonable cause and to penalties; it is not relevant to whether the assessment period has run.
The UK Mirror: HMRC Discovery Windows Run to Their Own Clock
British practitioners frequently reassure clients by reference to HMRC's time limits, and the comparison is instructive because it runs the opposite way. HMRC's ordinary assessment window under the Taxes Management Act is four years, extending to six where the loss of tax was careless and twenty where it was deliberate, as set out in the compliance handbook guidance on assessing time limits.
For offshore matters Parliament created a twelve-year window in section 36A of the Taxes Management Act 1970. Crucially, however, that extended window is switched off where HMRC already held sufficient information — including information received automatically under exchange-of-information arrangements — to have made the assessment sooner. Britain, in other words, caps the offshore window and then removes it altogether when the revenue authority already had the data.
America does the reverse. There is no cap, no data-based shut-off, and no long-stop date. Consequently a dual filer can find their British years firmly closed whilst their American years for the very same income remain permanently open. Our analysis of the HMRC discovery assessment covers the British mechanics in full, and the professional commentary tracked by the ICAEW tax news service follows changes on that side.
Closing a Year Held Open by Section 6501(c)(8)
Only one thing stops Section 6501(c)(8) running against you: furnishing the information. Filing the missing form is therefore not merely a compliance tidy-up but the single act that converts an indefinite exposure into a three-year countdown. Because of that, sequencing matters more than speed.
Where returns were filed but foreign forms were omitted, and reasonable cause exists, the delinquent international information return submission procedures allow the forms to be submitted with a reasonable cause statement. Where returns themselves were missed or were materially wrong, the IRS Streamlined Filing Compliance Procedures provide three years of amended or delinquent returns, six years of foreign account reports and a non-wilful certification. Our IRS Streamlined Filing service and our FBAR and FATCA service handle both routes, and the full menu of options is summarised by the Internal Revenue Service in its guidance on options for taxpayers with undisclosed foreign financial assets.
Understand what these programmes do and do not achieve. They resolve penalties and they furnish the information, which starts the clock. However, the clock then runs three years from furnishing, so years cleaned up in 2026 remain open until 2029. Meanwhile the penalty regime is unforgiving: section 6038 imposes $10,000 per form per year with continuation penalties reaching $50,000, as the Internal Revenue Service confirms in its guidance on international information reporting penalties and its internal revenue manual on international penalties. Section 6038(c) additionally reduces your foreign tax credit, which matters most to high earners paying substantial British tax. Notably, the automatic penalty relief regime taking effect on 1 January 2027 expressly excludes Forms 5471, 3520 and 8938, so waiting for administrative mercy is not a strategy.
Worked Case Study: Fourteen Years Held Open by One Form
David is a US citizen who has lived in Manchester since 2010. He incorporated a small British consultancy company in 2011 and has owned it outright ever since. A British accountant prepared his company accounts and his self assessment returns faultlessly, and a separate preparer filed his American returns each year. Nobody ever mentioned Form 5471. All figures below are illustrative.
By 2026 David has filed fifteen consecutive American returns, every one on time. He assumes his exposure begins in 2023, and Section 6501(c)(8) says otherwise. In fact, because the section 6038 information was never furnished for any year, none of those fifteen years has ever started its assessment period. Every one of them is open.
The company itself is not the problem. Its profits were modest and the British corporation tax paid on them generated credits that covered the American charge. The problem lies elsewhere. In 2014 David sold a rental flat in Salford, realising a gain of roughly $180,000, and his preparer applied the foreign tax credit incorrectly, understating his American liability by about $31,000. Under section 6501(a) that year closed in 2018 and the error became permanently unassessable. Under Section 6501(c)(8), it did not close at all. In 2026 the Internal Revenue Service can still assess that $31,000, and with roughly twelve years of statutory interest running the figure is closer to $60,000 before any accuracy-related penalty.
Separately, the information return penalties are calculated at $10,000 per company per year. Across fifteen open years that is a headline exposure of $150,000, before continuation penalties.
Now apply subparagraph (B). David relied in good faith on qualified British and American preparers, neither of whom raised the foreign corporation reporting requirement, and he can evidence that reliance through his engagement letters and correspondence. If reasonable cause is established, Section 6501(c)(8) applies only to items related to the missing Form 5471. The Salford property gain is not such an item. Accordingly, that year reverts to the ordinary three-year rule, it is closed, and the $60,000 assessment disappears entirely. The same reasonable cause showing supports abatement of the information return penalties.
The lesson is precise. David's protection came not from the penalty argument that dominates most discussions, but from the statute of limitations argument buried in a single sentence of subparagraph (B).
Contact Us
If you own a British company, hold British investment funds, or have ever moved assets into a corporate structure, there is a real possibility that tax years you consider ancient are still legally open. Equally, if you are already planning a catch-up filing, the sequencing and the reasonable cause position should be settled before anything is submitted, because a filing made without asserting subparagraph (B) gives away an argument that cannot easily be recovered later.
TaxYork prepares American and British returns for high-net-worth clients in Britain, including full US tax return preparation for expats, catch-up filings and foreign company reporting such as Form 8858 for UK business owners. To review your open years, please book a consultation, email hello@taxyork.com or call 020 3488 8606.
Written by the TaxYork Expert Team — US-UK tax specialists.
*This article is for general information only and does not constitute tax advice. Tax rules change and their application depends on individual circumstances. You should obtain professional advice tailored to your own position before acting on anything set out above.*