Do US capital losses expire if I have missed US tax returns?

No. For individuals, a net capital loss above the annual deduction limit carries forward with no expiry date. However, the carryover is reduced every year by capital gains it absorbs and by the annual allowance treated as used, whether or not a return was filed. You must rebuild the carryover through each unfiled year before using the remaining balance on current or streamlined returns.

How much capital loss can I deduct against other income each year?

IRS Tax Topic 409 states that the excess of capital losses over capital gains you can deduct against other income is the lesser of $3,000, or $1,500 if married filing separately, and your total net loss. Capital losses first offset capital gains without limit. Anything left after the annual allowance carries forward to later years, keeping its short-term or long-term character.

Can a streamlined filing use losses from years before the three-year window?

Yes. The Streamlined Foreign Offshore Procedures require returns for the most recent three years, but a carryover from an earlier loss year flows into the first of those returns on Schedule D. The balance must be computed year by year from the loss year, and you should keep full records, because the IRS can recompute earlier years to verify a carryover claimed in an open year.

Why is my US capital loss different from my UK loss on the same shares?

US gains and losses are measured in dollars. Your US basis is fixed at the exchange rate on the purchase date and proceeds are translated at the sale date rate, so exchange movements change the result. A sterling loss can become a larger dollar loss, a smaller one, or even a dollar gain. The UK computes the same disposal in sterling, so the two figures often differ.

What is the time limit for claiming a UK capital loss?

GOV.UK guidance says you do not have to report a capital loss straight away, but you can claim it up to 4 years after the end of the tax year in which you disposed of the asset. Once claimed, unused UK losses can be carried forward against future gains. The UK claim is separate from the US carryover and is calculated independently in sterling.

Can losses on UK funds treated as PFICs join my US capital loss carryover?

Not automatically. Under section 1291, gain on a PFIC disposal is treated as an excess distribution, taxed as ordinary income with a deferred tax and interest charge for earlier years, and a capital loss carryover does not offset it like an ordinary capital gain. Section 1291 does not provide a loss mechanism itself, so loss treatment depends on any QEF or mark-to-market election and needs separate analysis.

Missed US Tax Returns: Capital Loss Carryover Guide

Missed US tax returns do not wipe out capital losses you realised in those years: for individuals, a net capital loss that exceeds the annual deduction limit carries forward indefinitely. The catch is that the carryover is consumed every year, whether or not you filed, so it must be rebuilt year by year from the loss year through every unfiled year before it can be used on the returns you now submit. For a US citizen investor living in the UK who took heavy losses in a market downturn or on a failed private investment, getting that schedule right is often worth more than any other line on the catch-up filing.

In the returns we prepare for high-net-worth US citizens in London and across the UK, the failure mode we see most often is simple: the client remembers a large loss, assumes the full figure is still available, and drops it into the first year of a streamlined submission. That figure is almost always overstated. This guide explains the US mechanics, walks through a full six-year carryover schedule with three unfiled years, and sets out the documentation pack you need if the IRS asks you to prove the number.

What is a capital loss carryover under US tax law?

A capital loss carryover is the part of a net capital loss that could not be deducted in the year it arose and is instead treated as a capital loss in the following year. The IRS states in Tax Topic 409 at https://www.irs.gov/taxtopics/tc409 that if your capital losses exceed your capital gains, the excess you can claim against other income is the lesser of $3,000 ($1,500 if married filing separately) or your total net loss, and that a net capital loss above this limit can be carried forward to later years.

The statutory basis is in two sections of the Internal Revenue Code. Section 1211(b), at https://www.law.cornell.edu/uscode/text/26/1211, limits the deduction of capital losses for individuals to capital gains plus the annual allowance. Section 1212(b), at https://www.law.cornell.edu/uscode/text/26/1212, provides the carryover for taxpayers other than corporations. Unlike the corporate rule, there is no fixed number of years after which an individual's carryover expires. IRS Publication 550, at https://www.irs.gov/publications/p550, describes the carried-over amount as treated as if it were incurred in the next year.

Annual limit against ordinary income: $3,000, or $1,500 if married filing separately (IRS Tax Topic 409).
Carryforward period for individuals: no expiry; the loss rolls forward until it is used.
Losses first offset capital gains in full, without any cap, before the annual allowance is applied to other income.
Short-term and long-term character is preserved in the carryover.
The carryover is computed on the Capital Loss Carryover Worksheet in the Schedule D instructions.

Why short-term and long-term character matters in the carryover

Under Tax Topic 409, a gain or loss is generally long-term if you held the asset for more than one year and short-term if you held it for one year or less, counting from the day after acquisition up to and including the day of disposal. Section 1212(b)(1) then provides that the excess of the net short-term capital loss over the net long-term capital gain becomes a short-term capital loss in the following year, and the excess of the net long-term capital loss over the net short-term capital gain becomes a long-term capital loss in the following year.

Character matters because it decides which gains the loss meets first in later years. A short-term carryover is netted against short-term gains, which would otherwise be taxed at ordinary rates, while a long-term carryover is netted against long-term gains that would otherwise qualify for the preferential rates. The worksheet also applies the annual deduction to short-term losses before long-term losses, which is why the two carryover buckets shrink at different speeds. Collapsing them into a single number, as many self-prepared catch-up returns do, can misstate both the tax and the carryover that flows into the next year.

How do missed US tax returns affect a capital loss carryover?

This is the heart of the problem. A carryover is not a bank balance that sits untouched while you are out of compliance. Each year, the law treats the carryover as a capital loss of that year. It absorbs any capital gains you realised, and up to the annual allowance of what remains is treated as used against other income. Section 1212(b)(2) makes this explicit: the amount allowed under section 1211(b), limited by adjusted taxable income, is treated as a short-term capital gain for the purpose of computing the next carryover. In plain terms, the carryover shrinks each year by the gains it absorbed and by the allowance it was treated as using.

The fact that no return was filed for a year does not stop that consumption. When we rebuild the history for a client, we compute each unfiled year as if the return had been correctly prepared, because that is what the statute's year-by-year structure requires. Gains realised in unfiled years, including gains from selling UK shares, US-listed funds, a property or a business interest, all eat into the carryover even though no Schedule D ever reported them.

Myth: US capital losses are use it or lose it. Fact: for individuals they do not expire.
Myth: if I did not file, the loss is still sitting there in full. Fact: it was consumed by each year's gains and allowance whether or not you filed.
Myth: I only need the three streamlined years. Fact: the opening carryover for the first streamlined year depends on every year back to the loss year.
Myth: a sterling loss is automatically a US loss. Fact: US gains and losses are measured in dollars and can differ sharply.

Running the Capital Loss Carryover Worksheet year by year

The Schedule D instructions at https://www.irs.gov/instructions/i1040sd contain the Capital Loss Carryover Worksheet. Its first line takes the prior year's taxable income from Form 1040 line 15, entered in parentheses if it would have been a loss. Line 2 takes the prior year's net loss from Schedule D line 21 as a positive number. Line 4 is the smaller of that loss and the combined figure from lines 1 and 2, which is the amount treated as used. The worksheet then allocates that used amount first against the net short-term loss, producing the short-term carryover on line 8, and applies any balance against the net long-term loss, producing the long-term carryover on line 13.

Two practical consequences follow. First, if a year's taxable income was very small or negative, less than the full annual allowance may be treated as used, so a larger carryover survives. This can matter for a UK resident whose US taxable income was reduced in a given year. Second, the worksheet must be completed for each year in sequence: you cannot compute Year 4's opening carryover without Year 3's Schedule D, and you cannot compute Year 3's without Year 2's. For unfiled years, we prepare pro forma Schedule D and worksheet computations and keep them in the file, even though those returns are not submitted as part of a three-year streamlined package.

Worked example: a six-year carryover schedule with three unfiled years

The following is an illustration only, with round figures chosen to show the mechanics. Assume a single US citizen living in London whose US taxable income is comfortably above the annual allowance every year, so the full $3,000 is treated as used each year. Years 1 to 3 were never filed. Years 4 to 6 are the three years filed under the Streamlined Foreign Offshore Procedures. All amounts are in US dollars after translating each purchase and sale at the relevant exchange rate.

Year 1 (unfiled): a failed private investment produces a $180,000 long-term loss and a market sell-off produces a $20,000 short-term loss. No gains. Net loss $200,000; $3,000 treated as used, taken first from the short-term side. Carryover out: short-term $17,000, long-term $180,000, total $197,000.
Year 2 (unfiled): a $5,000 short-term gain. Short-term netting: $5,000 less $17,000 gives a $12,000 net short-term loss; long-term stays at $180,000. Net loss $192,000; $3,000 used. Carryover out: short-term $9,000, long-term $180,000, total $189,000.
Year 3 (unfiled): a $40,000 long-term gain on a US-listed fund. Long-term: $40,000 less $180,000 gives $140,000 net loss; short-term loss $9,000. Net loss $149,000; $3,000 used. Carryover out: short-term $6,000, long-term $140,000, total $146,000.
Year 4 (streamlined): a $60,000 long-term gain. Long-term: $60,000 less $140,000 gives $80,000 net loss; short-term loss $6,000. Net loss $86,000; $3,000 deducted. Carryover out: short-term $3,000, long-term $80,000, total $83,000.
Year 5 (streamlined): a $10,000 short-term gain and a $50,000 long-term gain. Short-term: $10,000 less $3,000 gives a $7,000 net gain. Long-term: $50,000 less $80,000 gives a $30,000 net loss. Net loss $23,000; $3,000 deducted. Carryover out: short-term nil, long-term $20,000.
Year 6 (streamlined): a $45,000 long-term gain. Long-term: $45,000 less the $20,000 carryover gives a $25,000 net long-term gain, which is taxable. The carryover is fully used.

Now compare the shortcut. If the client had ignored Years 1 to 3 and entered the original $200,000 as the carryover into Year 4, the streamlined returns would have claimed $54,000 of losses that no longer existed. That $54,000 is exactly the $45,000 of gains absorbed in Years 2 and 3 plus $9,000 of annual allowance treated as used across Years 1 to 3. On these facts, the overstated carryover would have sheltered the entire Year 6 gain and part of Year 5, understating tax on a submission whose whole purpose is to certify full and accurate reporting. The correct opening carryover for Year 4 is $146,000, split $6,000 short-term and $140,000 long-term.

Using earlier losses in a streamlined submission

The IRS page for taxpayers residing outside the United States, at https://www.irs.gov/individuals/international-taxpayers/us-taxpayers-residing-outside-the-united-states, requires delinquent or amended tax returns, with all required information returns, for each of the most recent three years for which the US return due date (or properly extended due date) has passed, together with delinquent FBARs for the most recent six years and a signed Form 14653 non-willful certification. Losses from years before the three-year window are not reported on returns you file, but the carryover they generate flows into the first streamlined year on Schedule D line 6 (short-term) and line 14 (long-term).

Because a carryover from an earlier unfiled year appears on the first streamlined return without any matching filed return behind it, we attach a short explanatory statement setting out the loss year, the nature of the loss and a summary of the year-by-year schedule. This is not a formal IRS requirement for every case, but in our experience it makes the figure intelligible to anyone reviewing the return and reduces the chance of a correspondence query. If the late FBARs sit alongside the returns, they are filed through FinCEN's BSA E-Filing System as part of the streamlined package; the old Delinquent FBAR Submission Procedures page has been withdrawn by the IRS and should not be treated as a separate route.

Can the IRS examine a closed year to verify a carryover?

Yes, in substance. The statute of limitations on assessment protects you from additional tax being assessed for a closed year, but it does not stop the IRS from recomputing a closed year to determine the correct amount of a loss carried into an open year. The Internal Revenue Manual, in its guidance on loss carryforwards at https://www.irs.gov/irm/part4/irm_04-011-011, states that the Service may redetermine correct taxable income in a closed year to ascertain the amount of a loss or the amount absorbed in that year. That passage is written for net operating losses, and the same principle is generally understood to apply to other carryovers, including capital loss carryovers. For a year that was never filed, the assessment period generally has not begun to run at all.

The practical consequence is that the burden of proof sits with you. If a streamlined return is later selected for examination and the carryover is questioned, you will need to show the original cost, the date and proceeds of each disposal in the loss year, and every gain in the intervening years. A carryover you cannot substantiate can be reduced or disallowed in the open year, even though the loss itself happened long ago.

The currency trap: a sterling loss is not always a dollar loss

The IRS page on foreign currency at https://www.irs.gov/individuals/international-taxpayers/foreign-currency-and-currency-exchange-rates states that amounts on a US return must be expressed in US dollars, using the exchange rate prevailing when you receive, pay or accrue the item. For an asset bought and sold in sterling, the US cost basis is fixed in dollars at the purchase date and the proceeds are translated at the sale date. The UK loss you see on your broker statement can therefore be a larger US loss, a smaller one, or a US gain.

An illustration, with assumed exchange rates only. Suppose you bought UK shares for 100,000 pounds when the assumed rate was $1.60, giving a US basis of $160,000, and sold them for 80,000 pounds when the assumed rate was $1.25, giving proceeds of $100,000. The sterling loss is 20,000 pounds, but the US loss is $60,000. Reverse the currency move: bought for 100,000 pounds at an assumed $1.25 ($125,000) and sold for 90,000 pounds at an assumed $1.45 ($130,500). The sterling loss is 10,000 pounds, yet the US result is a $5,500 gain. In a downturn year, the dollar figure is the one that drives the carryover, and we recompute every disposal in dollars rather than converting the net sterling result. Gains and losses on holding foreign currency itself are a separate category of their own and are not part of the capital loss carryover discussed here.

Wash sales and PFIC losses: two limits on usable losses

The wash sale rule can reduce the loss that goes into the schedule in the first place. The Schedule D instructions state that you cannot deduct losses from wash sales unless you are a dealer in stock or securities, and Publication 550 explains that a wash sale occurs when you sell at a loss and acquire substantially identical securities within 30 days before or after the sale. The disallowed loss is added to the basis of the replacement shares and their holding period includes that of the shares sold. Investors who sold in a downturn and bought back quickly, including through a UK account, often find part of the loss deferred rather than available in the loss year. The UK has its own separate 30-day share matching rule, and the two rules do not produce the same answer.

Losses connected with passive foreign investment companies need particular care. Many UK-domiciled pooled funds, such as OEICs, are treated as PFICs for US purposes. Under section 1291, at https://www.law.cornell.edu/uscode/text/26/1291, gain on disposing of PFIC stock is treated as an excess distribution: it is allocated across the holding period, the part allocated to the current year is taxed as ordinary income, and the parts allocated to earlier years are taxed through a deferred tax amount with an interest charge. Your capital loss carryover does not offset those amounts the way it would offset an ordinary capital gain. Section 1291 does not itself provide a loss mechanism, and how a loss on a PFIC is treated depends on whether a QEF or mark-to-market election was in place. We therefore separate PFIC positions from the main carryover schedule and do not assume a fund loss simply joins the Schedule D pool.

The UK side in brief: claim the loss within the time limit

UK capital losses follow different rules. GOV.UK guidance at https://www.gov.uk/capital-gains-tax/losses explains that you do not have to report a loss straight away, but you can claim it up to 4 years after the end of the tax year in which you disposed of the asset. Once claimed, unused losses can be carried forward against future gains. A UK loss claim is separate from the US carryover and is computed in sterling, so the two figures will rarely match. Keep the UK claim and the US schedule as two distinct workpapers, and do not assume that a loss preserved in one system is automatically preserved in the other.

The documentation pack for a rebuilt carryover

Because the IRS can look behind the carryover, the schedule is only as strong as the records behind it. For clients with missed US tax returns and a historic loss, we assemble the following pack before the first streamlined return is signed.

Contract notes or broker statements showing the purchase date, quantity and cost of every position sold at a loss, and the sale date and proceeds.
For a failed private investment: subscription agreements, share certificates, capital call records and evidence of when and how the investment became worthless or was disposed of.
Exchange rates used for each purchase and sale date, with the source recorded.
Annual broker statements for every intervening year, to evidence all gains that absorbed the carryover.
Pro forma Schedule D and Capital Loss Carryover Worksheets for each unfiled year back to the loss year.
Wash sale review for repurchases within 30 days before or after each loss sale.
A PFIC analysis identifying any fund holdings and the treatment applied to them.
The explanatory statement attached to the first streamlined return summarising the schedule.

Where records are incomplete, we reconstruct from bank statements, platform archives and annual tax packs, and we note any estimate clearly. A carryover built on reconstructed but documented figures is defensible; one built on memory is not.

Practical sequence for high-net-worth investors

Our preparation sequence runs from the oldest relevant year forward. We identify the loss year, recompute every disposal in dollars, apply the wash sale review, isolate PFIC positions, and run the worksheet through each unfiled year to produce the opening carryover for the first streamlined year. Only then do we prepare the three streamlined returns, carrying the short-term and long-term balances through Schedule D, and file the six years of FBARs and the Form 14653 certification. The schedule is kept on file for as long as any part of the carryover is being used, because every future return that relies on it depends on the same history.

For investors with large historic losses, the sums at stake are significant in both directions. Understate the carryover and you pay tax on gains the law would have sheltered; overstate it and you undermine a filing that rests on a certification of complete and accurate reporting. Getting the year-by-year computation right is the core of the compliance work, not an afterthought.