Can I claim capital allowances I missed

Q: How long do I have to add a missed claim?

TaxpayerTime limit to make or amend the claimAuthority Sole trader, partnership or individual landlordThe normal time limit for amending the return: 12 months after the filing date, which is normally 31 January after the end of the tax yearTMA 1970 s9ZA; CA11130 CompanyThe latest of: 12 months after the filing date; 30 days after an enquiry into the return is completed; 30 days after HMRC amends the return after an enquiry; 30 days after any appeal is finally determinedFA 1998 Sch 18 para 82(1); CA11140 For income tax the filing date under section 9ZA(3) is 31 January after the tax year, or three months after the notice to file if that notice was issued after 31 October. So a 2024 to 2025 return, with a filing date of 31 January 2026, can be amended until 31 January 2027, while the 2023 to 2024 window closed on 31 January 2026. HMRC's own example at CA11130 runs the same way for 2017 to 2018. A company's return is due 12 months after the end of the accounting period, so in most cases the capital allowances window ends two years after the period end (CA11140). Paragraph 82(3) means a capital allowances claim made within that window is valid even if the ordinary time limit for amending the return has passed. An enquiry limited to an earlier amendment that only changed capital allowances does not extend the window (paragraph 82(4)). For the mechanics of filing the amendment, see how to amend a company tax return and amending a Self Assessment return.

Q: How does a late claim work in practice?

Illustration only. Brook Ltd has a 31 March year end. In February 2024 it bought machinery for £60,000 and forgot to claim. In October 2026 its adviser spots the omission. Year to 31 March 2024. Filing date 31 March 2025, so the claim window closed on 31 March 2026. The annual investment allowance that would have relieved the full £60,000 is lost. Year to 31 March 2025. Filing date 31 March 2026, so claims can be made until 31 March 2027. Brook Ltd still owned the machinery in that period, so it amends that return to add £60,000 to the main pool and claims writing down allowance at 18%, which is £10,800. Year to 31 March 2026. Already filed, so within 30 days it amends this return too, claiming 18% on the higher pool balance brought forward. Later years. The rest of the pool is relieved at 14% a year from the year beginning 1 April 2026.

Capital allowances are only given if you claim them in a tax return, but a missed claim can be added by amending that return within its time limit: 12 months after the 31 January filing date for income tax, and normally 12 months after the filing date for a company. Once that window has closed, the annual investment allowance and first year allowances for that period are lost, but plant you still own can usually go into the pool in a later open year and attract writing down allowances from then on.

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How do capital allowances have to be claimed?

There is no separate claim form for most allowances. GOV.UK says you claim on your Self Assessment return as a sole trader, on the partnership return for a partnership, and on the Company Tax Return for a limited company, which must include a separate capital allowances calculation. HMRC’s Capital Allowances Manual adds two points that affect missed claims:

for a company, the claim, any amendment and any withdrawal must be made in the return or an amended return for the accounting period concerned, and the amount claimed must be specified (CA11140);
for a partnership, the partnership claims, not the individual partners (CA11130).

Because allowances are claims, leaving them out of a return is not an error HMRC will correct for you. The figure in the return is the claim.

How long do I have to add a missed claim?

Taxpayer	Time limit to make or amend the claim	Authority
Sole trader, partnership or individual landlord	The normal time limit for amending the return: 12 months after the filing date, which is normally 31 January after the end of the tax year	TMA 1970 s9ZA; CA11130
Company	The latest of: 12 months after the filing date; 30 days after an enquiry into the return is completed; 30 days after HMRC amends the return after an enquiry; 30 days after any appeal is finally determined	FA 1998 Sch 18 para 82(1); CA11140

For income tax the filing date under section 9ZA(3) is 31 January after the tax year, or three months after the notice to file if that notice was issued after 31 October. So a 2024 to 2025 return, with a filing date of 31 January 2026, can be amended until 31 January 2027, while the 2023 to 2024 window closed on 31 January 2026. HMRC’s own example at CA11130 runs the same way for 2017 to 2018.

A company’s return is due 12 months after the end of the accounting period, so in most cases the capital allowances window ends two years after the period end (CA11140). Paragraph 82(3) means a capital allowances claim made within that window is valid even if the ordinary time limit for amending the return has passed. An enquiry limited to an earlier amendment that only changed capital allowances does not extend the window (paragraph 82(4)). For the mechanics of filing the amendment, see how to amend a company tax return and amending a Self Assessment return.

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What is lost for good if I miss the deadline?

Some allowances can only be claimed for the period in which the expenditure was incurred. GOV.UK lists them as the annual investment allowance, 100% first year allowances, the super deduction and special rate first year allowance, full expensing and the 50% first year allowance, and the 40% first year allowance. Section 51A(2) of the Capital Allowances Act 2001 makes the same point for the annual investment allowance, and CA23085 confirms that an unused allowance cannot be carried forward.

If the return for the period of purchase can no longer be amended, those allowances for that spending are gone.

What can still be claimed in a later year?

Writing down allowances are more forgiving. GOV.UK says that if you do not claim the full value as an annual investment allowance or first year allowance, you can claim using writing down allowances at any time as long as you still own the item. The pooling rules in section 58 support this: expenditure cannot be allocated to a pool for a period before the one in which it was incurred, it cannot be allocated in a period in which you do not own the asset, and it cannot be allocated twice. Nothing requires it to be allocated in the year of purchase.

So the practical fix for a closed year is to allocate the unclaimed cost to the main pool or special rate pool in the earliest period whose return is still open, and claim writing down allowances from there. The relief comes more slowly, at the main rate of 14% for chargeable periods beginning on or after 1 April 2026 for companies and 6 April 2026 for income tax, or 18% for earlier periods, and 6% for the special rate pool (CA23220).

Can overpayment relief or a late claim rescue it?

Overpayment relief does not help. HMRC’s Self Assessment Claims Manual at SACM12075 says relief is not due where the excess arises from a failure to make a claim or from failing to allocate expenditure to a capital allowances pool. Its example is a trader who forgot to claim on a car: the omitted interest could be relieved, the capital allowances could not.

For companies, paragraph 82(2) lets HMRC allow a later claim, following Statement of Practice 5/2001. CA11140 says HMRC should only do so where circumstances beyond the company’s control prevented a timely claim, and it rules out a change of mind, hindsight, and oversight or error by the company or its advisers. A forgotten claim will almost never qualify.

What if later returns have already been filed?

A claim for an earlier period changes the pool carried forward, so the allowances for later periods change too. For a company, paragraph 83 gives it 30 days to amend any later return affected; if it does not, HMRC can amend the return by written notice, and the company has 30 days to appeal (CA11140). The normal amendment time limits do not block these consequential changes. An individual adding a claim to an earlier year should likewise check whether later open returns carried forward the wrong pool balance.

Why do missed claims on fixtures cause bigger problems?

For fixtures in a building transferred on or after 1 April 2014 (corporation tax) or 6 April 2014 (income tax), a buyer can only claim if the seller has pooled its own expenditure on those fixtures. CA26476 says pooling includes claiming the annual investment allowance or a first year allowance, there is no fixed time limit, but the seller must pool in a period in which it is still treated as owning the fixture. A business planning to sell property on which it never claimed should pool the fixtures in an open year before completion, or the buyer loses the allowances for good. See section 198 elections for the rest of that process.

How does a late claim work in practice?

Illustration only. Brook Ltd has a 31 March year end. In February 2024 it bought machinery for £60,000 and forgot to claim. In October 2026 its adviser spots the omission.

Year to 31 March 2024. Filing date 31 March 2025, so the claim window closed on 31 March 2026. The annual investment allowance that would have relieved the full £60,000 is lost.
Year to 31 March 2025. Filing date 31 March 2026, so claims can be made until 31 March 2027. Brook Ltd still owned the machinery in that period, so it amends that return to add £60,000 to the main pool and claims writing down allowance at 18%, which is £10,800.
Year to 31 March 2026. Already filed, so within 30 days it amends this return too, claiming 18% on the higher pool balance brought forward.
Later years. The rest of the pool is relieved at 14% a year from the year beginning 1 April 2026.

Which mistakes should you avoid?

Counting the 12 months from the date the return was submitted rather than from the filing date.
Trying to claim the annual investment allowance in a later year for spending in a closed year.
Making an overpayment relief claim for missed allowances.
Forgetting to amend later returns after changing an earlier pool.
Allocating cost for an asset already sold before the open year, which section 58(4) does not allow.
Leaving fixtures unpooled before selling a building.

For choosing deliberately how much to claim, see claiming less than full capital allowances, and for the allowances themselves see capital allowances explained.

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Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 24 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.