Can one US shareholder file Form 5471 for all the others?

Yes, within limits. The instructions allow one person to file Form 5471 and the applicable schedules for other persons if that person has the same filing requirements as, or greater filing requirements than, the others. A Category 4 controller can therefore file for Category 5a minority holders, but a Category 5a holder cannot file for a Category 4 controller. Every person named in item H must still attach their own statement to their own return.

Does a UK limited company with US shareholders always count as a controlled foreign corporation?

No. The company is a controlled foreign corporation only if US shareholders, meaning US persons owning 10 percent or more of vote or value, together own more than 50 percent of the total combined voting power or the total value of the stock on any day of the company's tax year. Holders below 10 percent are ignored entirely. UK-resident non-US shareholders never count toward the more than 50 percent figure.

If I am both a Category 4 and a Category 5a filer, which box do I tick?

Only Category 4. The Item B instructions state that if you satisfy the requirements of both Category 4 and Category 5a filers, you check the box for Category 4 and leave the Category 5a box blank. Category 4 carries the greater filing requirements, so nothing is lost by suppressing the second tick. If you are also filing for others under the joint filers exception, you still check only the categories that apply to you.

What has to go in the statement if another shareholder files for me?

Four items. The name, address and EIN or reference ID number of the UK company. A statement that your filing requirements for that company have been or will be satisfied. The name, address and identifying number of the taxpayer on the return the information was filed with. And the IRS Service Center where that return was or will be filed, or e-file if it was filed electronically. Your Schedule P attaches to that statement.

Do my UK Company Tax Return and Companies House filings cover Form 5471?

No. Registering for and filing Corporation Tax with HMRC, as described at gov.uk/corporation-tax, and filing annual accounts and a confirmation statement at Companies House, are entirely separate obligations owed by the company in the UK. Form 5471 is owed by each US shareholder individually to the IRS and attaches to that person's own US income tax return. A clean UK filing history gives no protection against the section 6038 penalty.

What if the shareholder who was going to file leaves the business mid-year?

File your own. The multiple filers exception is permissive, not mandatory, so any shareholder can prepare and file a complete Form 5471 for their own category at any point. Duplicate filings for the same company are not penalised, whereas relying on a departed colleague who never filed leaves you exposed in your own right. Note that a departing controller can still be a Category 4 filer, because control is tested at any time during the year.

Form 5471: UK Company, Several US Shareholders

Form 5471 is filed shareholder by shareholder, not company by company. When a UK limited company has several US shareholders, each of them tests their own filing category, each of them can end up filing a different set of schedules for the same company, and the section 6038 penalty attaches to each of them individually. One shareholder may file a single form covering the others under the multiple filers exception, but only where that person has the same filing requirements as, or greater filing requirements than, the others, and only where every other person named on the form attaches a specific statement to their own return. Without that statement, a shareholder who relied on a colleague has, as far as the IRS record is concerned, filed nothing.

That last point is what catches founder teams. In the returns we prepare for UK companies held by three or four US persons, the most common failure mode is not a missed form. It is four people who each believed the form was handled, one form actually filed, and three US returns with nothing attached to them. The rules sit in the Instructions for Form 5471 at irs.gov/instructions/i5471, with the current December 2025 revision available in full at irs.gov/pub/irs-pdf/i5471.pdf, and the consequences are personal to each shareholder rather than to the company.

Does a UK Company With Several US Shareholders Trigger Form 5471?

Usually yes, and the test runs in two stages. First you identify who the US shareholders are. Second you ask whether those US shareholders together control the company. Neither stage looks at the company's turnover, its profitability or whether it has distributed anything. A dormant UK company with two US founders can be squarely in scope while a busy one with a single 9 percent US investor is not.

For Category 5 purposes the instructions define a US shareholder as a US person who owns, directly, indirectly, or constructively within the meaning of section 958(a) and (b), 10 percent or more of the total combined voting power or value of shares of all classes of stock of a controlled foreign corporation. A holder sitting below 10 percent is not a US shareholder for this purpose and does not count toward the control test at all.

A controlled foreign corporation, in turn, is a foreign corporation whose US shareholders own, on any day of the foreign corporation's tax year, more than 50 percent of either the total combined voting power of all classes of its voting stock, or the total value of the stock of the corporation. Both limbs matter independently. A UK company with a small founder voting class and a much larger non-voting or growth share class can comfortably fail the voting test and still be a controlled foreign corporation on value, which is a structure we see regularly in UK companies that have taken external investment.

A US person for these purposes includes a US citizen or resident individual, a domestic partnership and a domestic corporation, with the full definition set out separately for each filer category in the instructions.
Only holders of 10 percent or more count as US shareholders when you add up the more than 50 percent control figure.
UK-only shareholders are simply outside the numerator. They do not dilute the test, they just do not contribute to it.
The control test is met if it is satisfied on any single day of the company's tax year, not only at the year end.
Voting power and value are tested separately. Failing one limb and meeting the other still produces a controlled foreign corporation.
Ownership is measured directly, indirectly and constructively, so shares held through a UK holding company or an intermediate entity still count.

How Does Each US Shareholder Work Out Their Own Filing Category?

Category 4 is the control category. It covers a US person who had control of a foreign corporation during the annual accounting period of the foreign corporation. Control means that at any time during that person's tax year the person owns stock possessing more than 50 percent of the total combined voting power of all classes of stock of the foreign corporation entitled to vote, or more than 50 percent of the total value of shares of all classes of stock. The instructions also treat a person who controls a corporation that in turn controls another as controlling that second corporation, which matters where a UK trading company sits under a UK holding company.

Category 5 is the US shareholder category. In general it covers a person who was a US shareholder that owned stock in a foreign corporation that was a controlled foreign corporation at any time during the foreign corporation's tax year ending with or within the US shareholder's tax year, and who owned that stock on the last day in that year in which the foreign corporation was a controlled foreign corporation. There are three sub-types. Category 5a is defined simply as a Category 5 filer that is not a Category 5b or 5c filer, and that is where almost every individual US founder or minority holder in a straightforward UK company lands.

Categories 5b and 5c exist for a different problem. They implement the relief announced in sections 8.02 and 8.03 of Rev. Proc. 2019-40, published at irs.gov/irb/2019-43_IRB, for what the instructions call a foreign-controlled controlled foreign corporation, meaning a company that is only a controlled foreign corporation because of downward attribution from a foreign person. That is a multinational group issue, not a founder team issue. If your UK company is a controlled foreign corporation because actual US people own most of it, nobody in the group is a 5b or 5c filer.

Two further categories catch movement rather than steady state. Category 2 covers a US officer or director of a foreign corporation in respect of which a US person acquires a 10 percent stock interest, and Category 3 covers a person who acquires stock crossing the 10 percent threshold or disposes of enough stock to fall below it. In a founder team those categories bite in the year someone joins the cap table, exercises options over the threshold, or sells out. A shareholder can therefore be a Category 3 and a Category 5a filer in the same year, and both boxes are checked.

Why a Category 4 Filer Never Checks the Category 5a Box

Item B of Form 5471 asks the filer to indicate the category or categories that describe the person filing the return, and the general rule is that if more than one category applies you check all boxes that apply. There is one specific carve-out, and it is the one that applies to the controlling founder of a UK company. The instructions state that if you satisfy the requirements of both Category 4 and Category 5a filers, you check only the box for Category 4 and leave the box for Category 5a blank.

This is not a concession. Category 4 carries the heavier schedule set of the two, so suppressing the Category 5a box removes a duplicate label, not any work. The instructions add a second rule that founder teams routinely get wrong: if you file on behalf of other persons under the joint filers exception, you check only the category or categories that apply to you. You do not check the minority holders' categories on their behalf. Their categories are captured by their identification in item H, not by your Item B ticks.

Which Schedules Does Each Category Have to File?

This is the practical heart of a multi-shareholder UK company. Two people can own stock in the same company, receive the same accounts and file materially different returns. The instructions set out a Filing Requirements for Categories of Filers chart, reproduced on page 8 of the December 2025 revision at irs.gov/pub/irs-pdf/i5471.pdf, and the honest way to use it is to run it as a separate checklist, column by column, for each shareholder. The individual schedule instructions then restate the rule at the top of each schedule.

Schedule M, reporting transactions between the company and its shareholders and other related persons, must be filed by every US person described in Category 4. Category 5a filers do not file it.
Schedule B, Part I, listing US persons owning 10 percent or more of vote or value, must be completed by Category 3 and Category 4 filers.
Schedule I, the shareholder's pro rata share of subpart F income and other income from a corporate distribution, must be filed by or for each Category 4, 5a or 5b US shareholder. The instructions direct the person filing to send each such shareholder a copy of their own separate Schedule I so they can complete their return.
Schedule H-1 must be attached separately for each Category 4, 5a or 5b person that is an applicable corporation within the meaning of section 59(k) for corporate alternative minimum tax purposes.
Schedule P, the previously taxed earnings and profits accounts, must be completed separately by each Category 1a, 1b, 4, 5a or 5b filer.
Schedule O, reporting organisation, reorganisation and stock transactions, splits by part. Part I is completed by every US citizen or resident described in Category 2, and Part II by every US person described in Category 3.

The pattern that emerges for a UK founder company is that the controlling shareholder carries the company-level reporting and the related party disclosure, while the minority US shareholders carry the shareholder-level reporting. The blank form itself, at irs.gov/pub/irs-pdf/f5471.pdf, and the schedule index on the overview page at irs.gov/forms-pubs/about-form-5471, are worth having open alongside the chart when you allocate the work.

How the Multiple Filers Exception Actually Works

The instructions state it directly. With respect to any category of filer, one person may file Form 5471 and the applicable schedules for other persons if that person has the same filing requirements as, or greater filing requirements than, the other persons. Where you and one or more other persons must furnish information for the same foreign corporation for the same period, a joint information return containing the required information may be filed with your tax return or with the tax return of any one of the other persons.

Direction of travel is what governs. A US person described in Category 5 may file a joint form with a Category 4 filer or another Category 5 filer. A Category 5b filer may file jointly with a Category 4 or 5a filer or another Category 5b filer. A Category 5b filer and a Category 5c filer cannot file jointly at all, because they do not have the same filing requirements. For Category 3 filers, the required information may only be filed by another person having an equal or greater interest, measured in terms of the value or voting power of the stock.

Applied to a UK founder company, the controlling shareholder who is a Category 4 filer can file for the Category 5a minority holders, because Category 4 is the greater requirement. The reverse does not work. A 12 percent Category 5a holder cannot file on behalf of the 60 percent Category 4 controller, because the minority holder's filing requirements are lesser. If the person with the accountant and the appetite for the work is the minority holder, the exception simply is not available in that direction, and the controller has to file in their own name.

What Must the Statement Attached to Every Other Shareholder's Return Say?

The person who files completes item H on page 1 of the form, naming each person on whose behalf the information return is filed. Every person identified in item H, other than members of the filer's consolidated return group, must then attach a statement to their own tax return. The instructions specify exactly what that statement contains.

The name, address and EIN, or reference ID number, of the foreign corporation.
A statement that their filing requirements with respect to the foreign corporation have been or will be satisfied.
The name, address and identifying number of the taxpayer on the return with which the information was or will be filed.
The IRS Service Center where the return was or will be filed, entering e-file if the return was or will be filed electronically.

There is one exception. If the person filing Form 5471 on behalf of others is married to a person identified in item H and they are filing Form 1040 jointly, the statement does not have to be attached to that jointly filed return. That covers a husband and wife who both hold shares in the UK company, and it is the only relief of its kind in the section. Business partners, siblings and unmarried co-founders each attach their own statement.

The instructions then add a caution that is easy to miss. All persons identified in item H must complete a separate Schedule P if the person is a US shareholder described in Category 1a, 1b, 4, 5a or 5b, and in that case the Schedule P must be attached to the statement described above. So relying on the multiple filers exception is not doing nothing. It is preparing and filing a statement plus your own Schedule P with your own return, on your own due date.

Why Relying on Someone Else's Filing Leaves You Exposed

The instructions carry a note that ought to be pinned above every founder team's cap table. Any person required to file Form 5471 and Schedule J, M or O who agrees to have another person file the form and schedules for them may be subject to the penalties if the other person does not file a correct and proper form and schedule. Delegation does not transfer the obligation. It transfers the work while leaving the liability where it started.

The section 6038 penalty is a 10,000 dollar penalty imposed for each annual accounting period of each foreign corporation for failure to furnish the required information within the time prescribed. If the information is still not filed within 90 days after the IRS has mailed a notice of the failure, an additional 10,000 dollar penalty per foreign corporation is charged for each 30-day period, or fraction of one, during which the failure continues after the 90-day period expires, subject to a maximum of 50,000 dollars for each failure.

There is a separate and often more expensive consequence for anyone claiming foreign tax credits on UK corporation tax. A person who fails to file or report all of the required information within the time prescribed is subject to a reduction of 10 percent of the foreign taxes available for credit under sections 901 and 960, with an additional 5 percent reduction for each 3-month period, or fraction of one, during which the failure continues more than 90 days after the IRS mails notice, subject to the limits in section 6038(c)(2). Criminal penalties under sections 7203, 7206 and 7207 may also apply. Separately, section 6501(c)(8) keeps the assessment period on the whole return open until three years after the missing information is furnished to the IRS, so an unfiled Form 5471 leaves every other item on that year's return open too.

Notice what none of that is scaled to. The penalty is not proportionate to your shareholding, to the company's profit or to any US tax due. A 12 percent holder in a loss-making UK company faces the same headline exposure as the 60 percent controller. That asymmetry is the reason the item H statement is worth far more than the twenty minutes it takes to draft.

The Founder Team Fact Pattern: Three US Persons and No Category 4 Filer

The cap table we see most often in UK startups and boutique fund management businesses is not one dominant owner. It is three or four US persons holding roughly equal slices, sometimes alongside a UK co-founder. Assume, purely as an illustration, that shareholder A holds 30 percent, shareholder B holds 30 percent, shareholder C holds 25 percent and a UK-only co-founder holds the remaining 15 percent, all of one class of ordinary shares.

The US shareholders together hold 85 percent, so the company is comfortably a controlled foreign corporation. But no single person owns more than 50 percent of vote or value, so nobody is a Category 4 filer. All three US holders are Category 5a filers with identical filing requirements, which means any one of them may file for the other two under the multiple filers exception, in either direction. There is no default filer and no natural candidate. The obligation does not sit on the company at all. It sits on three separate Forms 1040.

A second consequence catches preparers who are used to controlled UK subsidiaries. Because Schedule M is a Category 4 schedule and there is no Category 4 filer in this structure, no Schedule M is required. Director loan account movements, management charges and shareholder recharges between the UK company and its US owners will not appear anywhere on this return. That is the correct answer under the instructions, but it needs saying out loud in the working papers, because the absence of a Schedule M in a file otherwise full of related party traffic looks like an omission when someone reviews it two years later.

What Happens When the Filing Shareholder Leaves Mid-Year

The multiple filers exception is drafted for a stable group. Founder teams are not always stable. The exception has no mechanism for a filer who resigns, is bought out, falls out with the others or simply stops answering emails in February. Your Form 5471, or your item H statement and Schedule P, attaches to your own income tax return and is due when that return is due, including extensions. Nothing about the other person's departure moves your date.

You may lose access to the US-basis trial balance, the earnings and profits workings and the tax pool history that the schedules are built from.
You cannot complete the item H statement without knowing the return with which the information was filed and the Service Center, or that it was e-filed.
A departing controller may still be a Category 4 filer for the year, because control is tested at any time during the year rather than at the year end, which means the person least motivated to help still carries the heaviest schedule set.
Your own Schedule P still has to be prepared for your own previously taxed earnings account, whether or not anyone sends you the company-level figures.
Due dates diverge across a founder team, because the automatic extension available to taxpayers living outside the United States and any further extension filed can put one shareholder's deadline well after another's.
A mid-year share transfer can add a Category 3 obligation for whoever crossed or fell below the 10 percent line, on top of the Category 5 obligation.

The recovery position is straightforward and underused. The exception is permissive, never mandatory. Any shareholder may abandon it at any point and file a complete Form 5471 in their own name for their own category. Two shareholders each filing a full form for the same UK company is not a penalty event. One shareholder filing nothing because they expected a colleague to act is. When the relationship is deteriorating, the cheap answer is almost always to file your own.

The preventative answer is governance. In the founder companies we work with, the Form 5471 arrangements go into writing alongside the shareholders agreement rather than living in a WhatsApp thread.

Name the filing shareholder for each accounting period in writing, and re-confirm it each year rather than assuming last year's arrangement rolls forward.
Require delivery of the complete filed Form 5471 with every schedule, to every other US shareholder, by a fixed date that precedes the earliest shareholder due date.
Require the filer to issue each Category 4, 5a or 5b person their own separate Schedule I and Schedule P, which the instructions already contemplate for Schedule I.
Require written confirmation of the Service Center, or of e-file status, so the item H statements can be drafted accurately.
Give every US shareholder a standing right to the underlying trial balance and earnings and profits workings so they can file independently if they need to.
Deal expressly with what happens if the filing shareholder exits, is removed or becomes unresponsive part way through the year.

The Minority US Shareholder Who Is Category 5 Only

The minority US shareholder in a UK company controlled by another US person is in an odd position. They file a materially thinner return than the controller. No Schedule M, no Schedule B Part I, none of the organisational reporting on Schedule O unless they crossed or fell below 10 percent in the year. What remains is the identifying information, the shareholder-level schedules including Schedule I and Schedule P, and whichever of the company-level schedules their column of the chart calls for.

That thinner set is genuinely easier to prepare, and it is also the reason minority holders are the ones most likely to have nothing on file. They are told, correctly, that the controller is filing. They are not told that they still owe an item H statement and a Schedule P attached to it. In practice we treat a Category 5a minority position as a two-page annual task that never gets skipped, rather than as something contingent on what another shareholder does.

Schedule P: A Separate PTEP Account for Each Shareholder

Schedule P reports the previously taxed earnings and profits in the US shareholder's annual PTEP accounts with respect to a controlled foreign corporation, in the company's functional currency in Part I and the shareholder's US dollar basis in that PTEP in Part II. A separate Schedule P must be completed by each Category 1a, 1b, 4, 5a or 5b filer. Any person who qualifies as one of those filers but is not filing the form under the joint filers exception must still complete Schedule P and attach it to the statement attached to their tax return.

The instructions make the reason explicit. If a US shareholder wholly owns the company, Schedule P should include the same information reported in column (e) of Schedule J, Part I. But if there is more than one US shareholder, the amounts reported on Schedule P with respect to each US shareholder might be different from the amounts reported on Schedule J. Schedule J is the company's accumulated earnings and profits. Schedule P is personal to the holder, and in a founder company the two will not reconcile line for line.

Two mechanical points cause most of the rework we see. A separate Schedule P is completed for each applicable separate category of income, with the code entered on line a, and where a shareholder has more than one category they must also file a Schedule P using the code TOTAL that aggregates all amounts across the other Schedules P. Separately, a Schedule P should not be completed for the section 951A category at all. Reclassified section 951A PTEP, and section 951A PTEP that is in the section 951A category, are reported on the Schedule P completed for the general category.

For a UK company the functional currency will normally be sterling, entered using the ISO 4217 code, and Part I is completed in sterling with Part II in US dollars. All exchange rates on the form are reported using the divide-by convention, rounded to at least four places, expressed as the units of foreign currency that equal one US dollar rather than the other way round. Rounding further is required where four places would materially distort the result.

Why this matters commercially: when the UK company finally distributes, each shareholder's own Schedule P history determines how much of their dividend is a recovery of previously taxed earnings rather than a fresh inclusion, and it drives the section 986(c) currency result on that recovery. Two shareholders with identical percentages can reach different answers because they bought in at different times, made different section 962 choices, or had different inclusion histories. There is no company-level shortcut for this.

A Worked Scenario: Four Owners of a London Company

The following is an illustration only, using assumed percentages to show how the pieces fit. A London-incorporated limited company with a 31 December accounting date has four shareholders throughout the year: shareholder A, a US citizen resident in London, holds 60 percent of the single class of ordinary shares. Shareholder B, a US citizen resident in New York, holds 18 percent. Shareholder C, a dual US and UK citizen resident in London, holds 12 percent. Shareholder D, a UK national with no US status, holds 10 percent.

Step one. Shareholders A, B and C are each US shareholders because each owns 10 percent or more of vote and value. Shareholder D is disregarded for this test. Together A, B and C hold 90 percent, which is more than 50 percent of both vote and value, so the company is a controlled foreign corporation for the whole year.

Step two. Shareholder A owns more than 50 percent of vote and value at all times during the year, so shareholder A is a Category 4 filer. Shareholder A also meets the Category 5a definition, but under the Item B instruction ticks only the Category 4 box and leaves Category 5a blank. Shareholders B and C are Category 5a filers. Shareholder D files nothing.

Step three. Because Category 4 carries the same or greater filing requirements than Category 5a, shareholder A may file one Form 5471 covering all three, naming shareholders B and C in item H. Shareholder A completes the company-level schedules plus Schedule M, and prepares a separate Schedule I and a separate Schedule P for each of A, B and C. Shareholder A then sends B and C their own Schedule I and Schedule P.

Step four. Shareholders B and C each attach to their own Form 1040 a statement giving the company's name, address and reference ID number, confirming that their filing requirements have been or will be satisfied, giving shareholder A's name, address and identifying number as the taxpayer on the return with which the information was filed, and naming the Service Center or entering e-file. Each attaches their own Schedule P to that statement. If shareholder C were married to shareholder A and they filed a joint Form 1040, no statement would be needed on that joint return.

Step five, the failure case. Suppose shareholder A files on time but shareholders B and C attach nothing. Shareholder A is compliant. Shareholders B and C have not satisfied section 6038 in their own right, because the exception is conditional on the item H statement being attached to their returns. Each of them is exposed to the 10,000 dollar penalty for that annual accounting period, to the escalating penalty if the failure continues after IRS notice, to the reduction in foreign taxes available for credit, and to an open assessment period on their entire return under section 6501(c)(8).

How the UK Side Interacts

There is no UK counterpart to any of this, and no UK filing discharges it. Registering the company and filing its annual accounts and confirmation statement under the process described at gov.uk/limited-company-formation, and registering for and filing the Company Tax Return described at gov.uk/corporation-tax, satisfies HMRC and Companies House and has no bearing whatever on section 6038. We regularly meet UK accountants who assume the US shareholders are covered because the CT600 is clean. They are not.

The UK statutory accounts are the starting point rather than the answer. The income statement, balance sheet and earnings and profits schedules on Form 5471 are prepared on US tax principles, so UK GAAP presentation, capital allowances, disallowed expenditure, share-based payment treatment and provisions all have to be recast before they land on the form. In our experience this is the single largest block of work in a founder company file, and it is work the Category 4 shareholder carries alone even though every US shareholder benefits from it.

The Companies House register of members and the shareholders agreement are the evidence base for the ownership entries. Note a real trap in the sequencing: Item C on page 1 asks for the total percentage of the foreign corporation's voting power owned directly, indirectly or constructively at the end of the corporation's annual accounting period, whereas the Category 4 control test looks at any time during the person's tax year. A founder who was diluted below 50 percent by a December funding round reports a year-end Item C figure under 50 percent and is still a Category 4 filer for that year.

Where the UK company has no EIN, a reference ID number is entered instead. It must be alphanumeric with no spaces or special characters, is limited to 50 characters, and must be used consistently from year to year for that company. In a multi-shareholder group this needs to be agreed centrally, because each shareholder who ever files independently must use the same reference ID number for the same UK company, and the same number has to appear on any related Form 8992 schedules. If a UK company in the group is genuinely dormant, the summary filing procedure in Rev. Proc. 92-70 is available and satisfies the reporting requirements of sections 6038 and 6046, with the top margin of the return labelled accordingly.

If a form has already gone in and is later found to be incomplete or incorrect, the instructions direct you to file a corrected Form 5471 with an amended tax return, using the amended return instructions for the return it was originally filed with, entering Corrected at the top of the form and attaching a statement identifying the changes. That is also the route for a minority shareholder who discovers that the statement they should have attached was never attached.

How We Handle This in the Returns We Prepare

Multi-shareholder UK companies are the files where an engagement letter earns its keep, because the question of who is filing for whom has to be settled before anyone starts on the schedules. Our sequence is deliberately boring.

Build the cap table on a day-by-day basis for the whole accounting period, not just the year end, because both the control test and the Category 3 tests are movement tests.
Categorise every US holder separately and in writing, applying the Item B rule that a Category 4 and Category 5a person checks only Category 4.
Decide explicitly whether the multiple filers exception is being used, confirm the direction is permissible, and record who is filing for whom.
Draft the item H statement text for each non-filing shareholder at the same time as the form itself, rather than leaving it to their personal return preparer to invent later.
Prepare a separate Schedule I and Schedule P for every Category 4, 5a and 5b person and issue them to that person with the statement text.
Diarise each shareholder's own return due date, including any extension, since that is the date their statement is actually due.
Where a shareholder relationship looks unstable, default to independent filing for that shareholder rather than to the exception.

The underlying point is simple enough to state and easy to get wrong. Form 5471 attaches to a person, not to a company. In a UK company with several US shareholders, the company can be entirely compliant in the UK, the form can be filed correctly and on time by one owner, and two other owners can still be sitting on an unfiled section 6038 obligation and an open assessment period on their entire US return. The fix costs a statement and a Schedule P. The failure costs 10,000 dollars a year each, before anything else is counted.