What is the deadline for filing an 83(b) election?

The Section 83(b) election must be filed with the IRS within 30 days of the date the restricted property is transferred to you. The period runs from transfer, not from the date you signed the paperwork or the date the board approved the issue, and the IRS treats it as unextendable. Confirm the current filing address and any electronic filing options on IRS.gov before you post, and retain proof of timely mailing.

Do I need a Section 431 election if I already filed an 83(b)?

Yes. The two elections are independent. Section 83(b) is a US federal election under the Internal Revenue Code; Section 431 is a UK election under ITEPA 2003 made jointly with your employing company. Filing one has no effect on the other jurisdiction. A US person who is UK resident and holds restricted securities normally needs both, made within their separate 30-day and 14-day windows.

Can you make a late Section 431 election?

No. The 14-day window from acquisition of the restricted securities is statutory and HMRC has no discretion to accept a late election. If the window closes, the shares remain within the restricted securities regime and later chargeable events, including the lifting of restrictions or a sale, can produce UK employment income rather than capital gain. Discuss remedial structuring with an adviser and check the current position on GOV.UK.

Are founder shares issued at nominal value still worth an election?

Usually yes. When shares are acquired at or near unrestricted market value there may be little or no immediate charge, which makes both elections cheap to make and valuable as protection. The elections fix the tax position at acquisition and remove later growth from the employment income regimes. The main exposure is valuation risk if a tax authority later argues the acquisition price understated market value.

How does the UK tax my shares if I move to London after incorporating in Delaware?

It depends on your residence at the relevant times, the terms on which the shares were acquired, and whether the shares are employment-related securities. UK residents are generally taxed on worldwide income and gains, subject to the rules applying to newly arrived and internationally mobile individuals. Because the residence-based apportionment rules are detailed and change, take advice on your specific dates and check current guidance on GOV.UK.

Will the US-UK tax treaty stop me being taxed twice on my equity?

The treaty and the domestic foreign tax credit rules are designed to relieve double taxation, but relief depends on the same income being recognised in a compatible period and characterised compatibly in both countries. Elections filed on different dates, or in one country only, can move income into non-overlapping years and strand credits. Plan the timing before acquisition rather than trying to reconcile the mismatch afterwards.

Double Taxation: 83(b) and Section 431 Elections

A US founder who is UK resident and holds restricted founder shares generally needs two elections, not one: a US Section 83(b) election filed with the IRS within 30 days of the share transfer, and a UK Section 431 election agreed with the employing company within 14 days of acquisition. Filing only one leaves an asymmetry that can produce double taxation, or at least a mismatch between when income arises in each country and when foreign tax credits are available to relieve it. Both elections do broadly the same thing: they accelerate the charge to the acquisition date on the unrestricted value of the shares, so that later growth is taxed as capital rather than employment income. The deadlines are short, run in parallel, and are unforgiving.

What does a Section 83(b) election actually do?

Under the default US rule, property transferred in connection with the performance of services is not taxed at transfer if it is subject to a substantial risk of forfeiture. Instead, the recipient is taxed when the forfeiture risk lapses, on the value at that later date, less anything paid. For a founder holding shares that reverse-vest over four years, that means a series of annual or monthly income events measured against a company valuation that, if the business succeeds, climbs sharply. Ordinary income tax and, where relevant, employment taxes are calculated on each tranche as it vests.

A Section 83(b) election reverses that default. The founder elects to be taxed at the moment of transfer on the excess of the then fair market value over the amount paid, disregarding the forfeiture restrictions. On a typical incorporation where shares are subscribed at nominal value and the company has no meaningful assets, that excess is usually nil or trivially small. The election therefore converts what would have been a stream of future ordinary income into a single, near-zero income event, and starts the capital gains holding period immediately.

The trade-off is that the election is irrevocable and the tax paid is not refunded if the shares are later forfeited or the company fails. In practice, for founders acquiring at or near market value, that risk is small relative to the exposure being eliminated. The IRS sets out the content requirements and filing mechanics; confirm the current filing address and the required statement contents on IRS.gov before you send anything, and keep evidence of timely posting.

What is a Section 431 election and why do UK founders make one?

The UK equivalent sits in the employment-related securities code in ITEPA 2003. Where an employee or director acquires shares that carry restrictions — reverse vesting, compulsory transfer provisions, leaver clauses, transfer restrictions, or anything else that depresses value — the shares are restricted securities. The initial charge is calculated by reference to the restricted value, which is lower than the unrestricted value. That looks helpful, but it comes with a long tail: later chargeable events, including the lifting or variation of restrictions and disposals, can bring the withheld value back into charge as employment income.

A Section 431 election, made jointly by the employee and the employer, disapplies the restrictions for tax purposes at acquisition. The employee is treated as acquiring the shares at unrestricted market value, accepts any resulting income tax charge up front, and takes the shares outside the restricted securities regime for the future. Growth thereafter falls into the capital gains code rather than being recharacterised as employment income on a later exit.

The parallel with 83(b) is close enough that practitioners often describe them as mirror elections, and the commercial logic is identical: pay a small, certain charge now to avoid a large, uncertain income charge later. The mechanics, however, differ in ways that matter. HMRC publishes the standard election forms and guidance on GOV.UK, and the election is made with the employer rather than filed with HMRC.

Why does the 30-day versus 14-day timing mismatch matter so much?

The single most common failure among US founders operating through a UK company is treating the 83(b) deadline as the deadline. It is the longer of the two. By the time a founder has spoken to a US accountant, obtained a valuation view and posted the 83(b) statement inside 30 days, the 14-day UK window has often already closed. There is no mechanism to reopen it. HMRC has no statutory discretion to accept a late Section 431 election, and the shares stay in the restricted securities regime permanently.

The mismatch is compounded by the different trigger points. The 83(b) clock runs from the date of transfer of the property. The Section 431 clock runs from the acquisition of the employment-related securities. In a clean subscription these coincide, but where shares are issued subject to conditions, allotted before entry in the register, or transferred from a founder holding company, the two dates can diverge. Documenting the acquisition date precisely, in writing, at the time is not administrative housekeeping — it is the evidential foundation for both elections.

The practical answer is to treat 14 days as the operative deadline for the whole exercise, and to prepare both elections before the shares are issued rather than after. Signed election forms, a contemporaneous valuation memorandum, and the board minutes recording the issue should be assembled as a single closing bundle.

Fix and document the acquisition date before issue, not retrospectively
Prepare the Section 431 election form and the 83(b) statement in draft before completion
Obtain a defensible valuation view of both restricted and unrestricted value at acquisition
Have the employing company countersign the Section 431 election on the day of acquisition
File the 83(b) statement by tracked post well inside the 30-day window and retain proof
Store both elections with the company secretarial records and the founder's personal tax file

What happens if I file the 83(b) but miss the Section 431 election?

This is the classic pattern for a US founder who relocated to London and kept a US adviser. The US position is clean: income is recognised at acquisition on a near-nil spread, the holding period starts, and future appreciation is capital gain for US purposes. The UK position is not. The shares remain restricted securities, and value that was suppressed by the restrictions remains liable to come back into charge as employment income when the restrictions lift or on disposal.

The consequence at exit is a characterisation clash. The UK treats a slice of the exit proceeds as employment income, potentially with National Insurance exposure and PAYE obligations for the company on readily convertible assets. The US, having accepted the 83(b), treats the entire gain as capital. Because the two countries are taxing the same economic amount under different heads and, frequently, in different periods, the foreign tax credit machinery does not always deliver clean relief. Income re-sourcing and treaty relief may help, but they are remedial and depend on facts.

There is also a compliance overhang. The UK employment income charge sits on the self assessment return and may create an employer reporting obligation through the annual employment-related securities return. A founder who never expected a UK employment income event at exit is unlikely to have budgeted the cash or the withholding, and the discovery frequently arrives during transaction due diligence, at the worst possible moment.

What happens if I make the Section 431 election but miss the 83(b)?

The reverse failure is less common but arguably more expensive. Without an 83(b), the US treats each tranche of shares as taxed when the substantial risk of forfeiture lapses, on the value at that date. A founder whose company raises successive priced rounds during the vesting period faces ordinary income on the appreciation between issue and each vesting date, with no liquidity to fund it. Meanwhile, the Section 431 election has already settled the UK position at acquisition.

The result is a timing mismatch running in the opposite direction. The UK charge, if any, arose in the year of acquisition. The US charges arise across the vesting schedule. Any UK tax paid at acquisition is unlikely to be creditable against US tax arising three years later, because credits generally have to be matched to the year in which the corresponding income is recognised. Carryback and carryforward rules exist and can rescue part of the position, but they are a poor substitute for aligning the events in the first place.

Where the US charge is significant and unfunded, founders sometimes explore restructuring the vesting terms. Changing the forfeiture conditions after the fact rarely produces a clean answer and can itself be a chargeable event on the UK side. Prevention is far cheaper than cure.

How do the two elections interact on a later exit?

Where both elections were made correctly, the exit is comparatively simple. Both countries treat the disposal as a capital event. The UK measures gain against the acquisition cost as increased by any amount charged to income under the Section 431 election. The US measures gain against basis, comprising the amount paid plus any amount included in income under the 83(b). The two cost bases should be close but are not automatically identical, particularly where the elections were priced off different valuation conclusions or where exchange rates moved between the acquisition date and the disposal date.

Currency is a persistent source of divergence. US basis and proceeds are computed in dollars; UK acquisition cost and disposal proceeds in sterling. A founder can face a US gain and a UK gain of materially different size on the same transaction purely because of exchange rate movement across a multi-year hold. Where the disposal proceeds include deferred consideration, earn-outs or rollover paper, the two systems apply different rules on when value is recognised and how contingent consideration is valued, widening the gap further.

Foreign tax credit planning at exit therefore starts with reconciling the two computations line by line, in both currencies, before any return is filed. Where the elections were properly paired, relief is usually achievable. Where one was missed, the reconciliation is where the damage becomes visible.

Which valuation should the elections be based on?

Both elections are only as robust as the valuation supporting them. The 83(b) election requires the fair market value at transfer, ignoring lapse restrictions. The Section 431 election operates on unrestricted market value. In an early-stage company with no revenue, no external round and no assets, the honest answer is often a nominal figure, but 'often' is not 'always'. If a priced round closed shortly before or after issue, if the company holds intellectual property of demonstrable value, or if a buyer has already made an approach, a nominal valuation will not survive scrutiny.

The two jurisdictions also apply different valuation conventions. HMRC's approach to share valuation for employment-related securities, including its willingness to engage on valuations in certain circumstances, is described in guidance on GOV.UK. US valuation practice for private company shares typically relies on an independent appraisal. Where the numbers differ, document why, and keep the working papers. A contemporaneous valuation memorandum prepared at acquisition is worth far more in a later enquiry than a reconstruction prepared under pressure years afterwards.

Record the valuation basis, date and preparer in a memorandum signed at acquisition
Identify any recent or imminent funding round and address its effect explicitly
Value both the restricted and the unrestricted position for UK purposes
Reconcile the sterling and dollar figures and record the exchange rate used
Retain the cap table as at the acquisition date, including options and convertibles

Do these elections apply to options, growth shares and phantom equity?

No, and the distinction matters. Section 83(b) applies to transfers of property. An unexercised option is generally not property for this purpose, so there is nothing to elect on until exercise. On exercise of an option into shares that are themselves subject to forfeiture, an 83(b) election becomes relevant to the shares acquired, and the 30-day clock runs from that exercise. Section 431 works the same way: the election attaches to the acquisition of restricted securities, which for an option holder is the exercise date, not the grant date.

Growth shares and other hurdle instruments are restricted securities in their own right and are frequently the subject of Section 431 elections, precisely because their value is concentrated in future appreciation above the hurdle. Phantom equity and cash-settled arrangements are not securities at all; they produce employment income when paid and neither election is available. Founders sometimes assume that because a colleague filed elections on their instrument, the same applies to a different instrument. It does not.

For US persons, the instrument choice carries further consequences beyond the elections, including how the UK scheme is characterised for US purposes and whether any UK tax-advantaged status is respected on the US side. It generally is not, which is a separate planning problem.

What reporting follows the elections in each country?

On the US side, the 83(b) election is a standalone statement filed with the IRS within the 30-day window, and the founder retains a copy with permanent records. The income recognised, if any, flows through Form 1040 for the year of transfer. A US person who is UK resident will also be considering the wider US information reporting suite, including the FBAR filed with FinCEN for foreign financial accounts and Form 8938 attached to the return where the specified foreign financial asset thresholds are met. Ownership of a foreign company can pull in Form 5471, with its own detailed schedules and substantial penalties for omission.

On the UK side, the Section 431 election is not filed with HMRC; it is made between employee and employer and retained. Any income tax arising is reported through PAYE where applicable or on the self assessment return. Separately, the employing company must register the share plan or arrangement and make an annual employment-related securities return covering reportable events. Missed annual returns attract penalties and are a routine finding in transaction due diligence.

Founders should also expect the elections to be requested in any future funding or exit process. Buyers and their advisers ask for copies as a matter of course. An unlocatable 83(b) or an unsigned Section 431 form becomes a warranty, an indemnity or a price adjustment.

How should a US founder sequence the whole exercise?

The practical sequence starts weeks before the shares are issued, not on the day. Confirm whether the founder is a US person and whether they are, or will shortly become, UK resident. Confirm which entity is issuing, whether the shares are employment-related securities, and whether the founder is an employee or director of a group company. Fix the restriction terms and the acquisition date. Obtain the valuation. Prepare both election documents. Only then issue the shares.

Where a founder is mid-relocation, the analysis becomes considerably more involved. The UK rules for internationally mobile employees apportion employment income by reference to periods of residence and duties, and the US rules on sourcing and credits interact with them imperfectly. Arrival and departure dates, split-year treatment and the timing of the share acquisition relative to the move all change the answer. This is the point at which generic guidance stops being useful and specific advice becomes essential.

Finally, calendar the deadlines the moment the acquisition date is fixed. Fourteen days and thirty days from a specific, documented date, with a named person responsible for each. The most expensive equity tax outcomes in cross-border practice are rarely caused by sophisticated errors. They are caused by a diary entry nobody made.

What should founders check before relying on any of this?

Tax law, filing addresses, valuation practice, reporting thresholds and rates change, sometimes with little notice and sometimes retrospectively in effect. Nothing in this article is a substitute for advice on your own facts. Before making or omitting either election, confirm the current position directly with IRS.gov and GOV.UK, and take advice from a qualified cross-border adviser who is competent in both systems rather than one adviser in each country working without reference to the other.

That last point deserves emphasis. The failures described here almost never arise because a US accountant or a UK accountant made a mistake within their own jurisdiction. They arise because nobody was looking at both sets of rules on the same document at the same time. For a UK-resident US-person founder, the elections are a single coordinated exercise with two filings, not two separate compliance items.

Where an election has already been missed, do not assume the position is unfixable without reviewing it. Depending on the facts, the acquisition date, the instrument, the residence history and the terms of the restrictions, there may be room to mitigate. But the analysis needs to happen well before an exit process starts, not during it.