Crypto in company accounts over 12 months: two CT600 returns

In short: Company accounts covering more than 12 months normally need two CT600 returns because a Corporation Tax accounting period cannot exceed 12 months. For supported crypto cases, Taxley, a UK online Corporation Tax (CT600) filing service, time-apportions accounts income and Part 8 amounts. Capital gains follow disposal dates. A fixed-rate Part 8 deduction is calculated for each tax period, including its remaining-value cap.

Check whether Taxley fits your company, or see filing prices.

Key facts (checked on 26 October 2026)

Why do long company accounts need two Corporation Tax returns?

The period covered by the accounts and the Corporation Tax accounting period are different concepts. Accounts can cover more than a year, but a CT accounting period cannot exceed 12 months. Where the company is within the charge throughout a normal long accounts period, that produces a 12-month return and a shorter return.

GOV.UK's accounting-period guidance explains the 12-month limit. Check the actual start of the company's Corporation Tax period: incorporation and the start of taxable activity need not coincide. The first company accounts guide explains those dates.

The examples below assume the company is within the charge throughout 1 February 2025 to 31 March 2026. That is 424 days inclusive. The first return covers 1 February 2025 to 31 January 2026, or 365 days. The second covers 1 February to 31 March 2026, or 59 days. No leap day falls within these dates.

Use those exact dates when checking an allocation. Dividing by an approximate number of months can produce different figures. A company's long statutory accounts do not become two separate sets of annual accounts simply because there are two tax returns.

Which crypto amounts does Taxley time-apportion?

Taxley uses time apportionment for supported miscellaneous crypto income and earning costs, the profits of a supported crypto trade, and supported Part 8 amounts. This is an allocation between CT accounting periods, not a new valuation of the tokens. Keep the classification decision separate from the period split.

CIRD13510 directs Part 8 allocations to the general rules in CTA 2010 s.1172. On the ordinary time basis, multiply the period-of-account amount by each CT period's days divided by total days.

HMRC accepts a transaction basis between accounting periods where it gives a more accurate result, as CTM01405 explains. Taxley uses the time basis for these supported calculations; it does not offer that transaction-based alternative. Do not describe the product's method as the only allocation the law can permit.

For Part 8, calculate the tax credit or debit before allocating it. An accounts write-down can differ from the tax debit where the values diverge. The Part 8 crypto guide explains the ratio adjustment, section 723 reversals and election rules.

How is miscellaneous staking income divided between the two CT600s?

Under the time basis, supported non-trading staking income and its appropriate earning costs are allocated using the same day fractions. Each return then includes its own net miscellaneous income in box 205. Costs must not also remain deducted from a trade or management expenses. The income guide explains that reconciliation.

Illustrative example: across the 424-day period, eligible rewards have receipt values totalling £4,240. Appropriate earning costs total £848, separately shown. There is no other income, trade, disposal, relief, brought-forward miscellaneous loss or capital allowance claim. The custody and holdings checks all pass.

A close company that simply holds investments is a close investment-holding company (CIHC), which pays the 25% main rate with no small profits rate or marginal relief: CTM03951. Non-trading staking is not a trade, so it does not by itself take the company out of that status.

If the company is not a CIHC, has no associated companies and no exempt distributions, both figures fall below their small-profits limits (the second reduced for its 59 days), so tax at 19% would be £554.80 and £89.68. See GOV.UK rates. The income allocation and the company's rate are separate questions.

How is a non-trading Part 8 impairment split?

A supported non-trading Part 8 debit is allocated between the CT periods, with each return separately reporting its current loss and any relief claimed. A loss arising is not the same as the amount used against profits. Unused amounts need their own carry-forward record, subject to the applicable investment-business conditions.

Illustrative example: use the same dates but a different company. It is a CIHC with a continuing investment business and a genuine qualifying Part 8 holding. It has £4,240 bank interest, £848 qualifying management expenses and a £4,240 deductible impairment. Tax and accounts values agree; there are no other crypto amounts, elections, disposals or earlier losses.

Assume claims use current losses as shown and the earlier unused loss is preserved. The remaining loss record after both periods is £730 + £118 = £848. It is not £848 newly arising in the second period. Tax is nil in each return; otherwise the CIHC main rate would be 25%, without marginal relief.

The claim and continuing-business conditions are in CIRD13540. The box distinctions follow HMRC's return guide. Do not include an impairment again as a capital loss.

Why can the 4% election need a different calculation in each period?

A fixed-rate deduction is subject to the tax written-down value available in each accounting period. The full first-period allowance can leave too little value for the short second-period allowance. Splitting a combined debit only by days would then allocate the wrong amounts. CIRD12910 explains the period-by-period cap.

Illustrative example: a supported non-trading investment-company holding has a valid 4% election, tax cost of £10,000 and opening tax written-down value of £420. It was acquired before this period; there are no purchases, sales or other crypto income or costs. Use the same 365-day and 59-day tax periods.

The first-period deduction is £10,000 × 4% = £400, leaving £20 tax value. The second-period amount before the cap is £400 × 59/365, approximately £64.66. Only £20 remains, so the deduction is £20. Taxley's supported investment-company calculation applies these separate limits. It does not apportion £420 as £361.56 and £58.44.

Taxley cannot yet apply this long-period fixed-rate route to crypto held for a trading or property business. Purchases or sales during an elected period also remain unsupported. These are precise calculation limits, not a claim that long accounts with crypto are generally outside the service.

Do capital crypto gains follow the same day fractions?

Capital disposals are allocated to the accounting period identified by the disposal date, rather than spreading the gain across the long accounts. This differs from the supported Part 8 allocation. HMRC CG14250 explains why the disposal date determines the company's tax accounting period.

For example, assume a capital investment token is sold on 15 March 2026 for £6,000 against allowable tax cost of £5,000, with no fees or other gains or losses. The £1,000 chargeable gain belongs wholly to the second CT period. Boxes 210 and 220 contain £1,000 there; neither contains part of that gain in the first return.

That example concerns a capital holding, not Part 8 or dealer stock. The Bitcoin guide covers capital treatment, while the crypto trading guide covers trading stock. Confirm the regime before applying a period allocation.

What must be checked before filing long accounts with crypto in Taxley?

Check both period dates, the crypto regime, the allocation working and each return's tax result. Taxley asks long-period non-trading Part 8 holdings about tax-basis differences and other crypto income or costs, and requires explicit write-down and reversal figures, including zero. Unsupported combinations remain outside the service even when the dates themselves are straightforward.

Other uncaptured amounts on a non-trading Part 8 holding, excluded token rights, unsupported mixed use, historical treatment conflicts and crypto amounts netted against other lines can prevent filing. A trading, property or mixed company's neither-use Part 8 loss remains unsupported. The separate guides define the other income and stock limits.

Review tax values and loss balances across the two computations rather than entering the full long-period amount twice. Check your company's fit and view pricing before preparing the filing.

Frequently asked questions

Can I put fourteen months of crypto income on one CT600?

Not as one Corporation Tax accounting period. A CT period cannot exceed twelve months. Establish the correct dates first, then allocate supported income and costs between the relevant periods rather than entering the entire long-period amount twice.

Is a month-based split the same as a day-based split?

Not necessarily. Months have different lengths, and leap days can change the fractions. The worked period uses 365 and 59 days out of 424. Use the actual inclusive day counts required for the period allocation.

Does a year-end Part 8 write-down all belong in the second return?

Not under Taxley's supported time-basis calculation. It first works out the period-of-account Part 8 amount and then allocates it. HMRC can accept a more accurate transaction basis in appropriate circumstances, but Taxley does not offer that alternative.

Does every short second return pay Corporation Tax at 19%?

No. Short periods have reduced rate limits, and CIHCs cannot use the small profits rate or marginal relief. Check company status, associated companies, taxable and augmented profits before deciding which rate applies to the second return.

Does a capital crypto sale in March get spread over both returns?

No. Establish its tax disposal date and use the corresponding CT accounting period. A March disposal in the worked example belongs to the second return. A Part 8 realisation or dealer sale follows its own regime instead.

Can an unused Part 8 loss disappear when the second return starts?

It should remain separately identifiable where the carry-forward conditions are met. The second return's current loss is distinct from the earlier balance. The example assumes the investment business continues and preserves the first period's unused loss.

Review your figures before you file, ideally with a qualified adviser.