How to claim group relief on a CT600 (CT600C)

In short: Group relief lets one UK company use another group company's loss for the same period. The two must be in a 75% group, and the claimant claims in its own Company Tax Return (CT600) with the CT600C page, with written consent from the company giving up the loss (GOV.UK: Completing the CT600C page). Taxley prepares and files the CT600, with the CT600C for UK 75% groups, for £39.95 with micro-entity accounts, and files the accounts at Companies House once the return is paid and the accounts are finished.

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Key facts (checked on 11 October 2026)

What is group relief for Corporation Tax?

Group relief moves certain losses and other amounts from one company to another in the same group, so the group pays tax on its overall result. The surrendering company gives up the loss; the claimant deducts it from its own taxable profits for the period the two accounting periods overlap.

The rules are in Part 5 of the Corporation Tax Act 2010. A company can surrender amounts such as a trading loss, a non-trading loan relationship deficit and a UK property business loss, among others listed in CTA 2010 s.99. HMRC's loss guidance describes it simply: you can choose to offset certain losses, including trading losses, against profits of other members of the group, instead of carrying the loss forward or back (GOV.UK: Work out and claim relief from Corporation Tax trading losses). A claimant doesn't have to take the whole amount: a claim can be for part of it (CTA 2010 s.137). Relief can't be given twice for the same amount. A payment between the companies for the relief, up to the amount surrendered, is ignored for tax (HMRC manual CTM80145). Carried-forward losses from earlier periods follow a separate set of rules in Part 5A, covered later.

Which companies count as a 75% group?

Two companies are in the same group if one is a 75% subsidiary of the other, or both are 75% subsidiaries of a third company. "75%" means owning at least 75% of the ordinary share capital, and being entitled to at least 75% of the profits available for distribution and of the assets on a winding up.

The share test comes from the general definition of a 75% subsidiary, and CTA 2010 s.151 adds the two economic tests for group relief: the parent must be beneficially entitled to at least 75% of the profits available for distribution to equity holders, and would be entitled to at least 75% of the assets available to them on a winding up. Ownership can be direct or through other companies, so a 90% holding of a company that holds 90% of another gives an indirect 81%. Both companies must also be "UK related": UK resident, or within the charge to Corporation Tax in another way, such as through a UK permanent establishment (HMRC manual CTM80150). A group of companies under common ownership by an individual isn't a group for this purpose: there has to be a parent company. Being in a group also makes the companies associated, which shares out the small profits rate limits; our guide to associated companies covers that.

How much group relief can a company claim?

No more than the lower of two figures for the period the two companies' accounting periods overlap: the surrendering company's unused loss for that overlap, and the claimant's unrelieved profits for it. Where both companies share a year end, the overlap is the whole year and the limit is simply the smaller figure.

CTA 2010 s.138 caps each claim at the lower of the unused part of the surrenderable amount and the unrelieved part of the claimant's available total profits. Both are measured for the overlapping period. Section 139 takes the proportion of the surrendering company's period that falls in the overlap and applies it to the amount surrendered, then deducts what earlier claims have already used, and section 140 does the same for the claimant's profits. Within the claimant's own return, current-period group relief comes after the company's own reliefs for that period and qualifying donations, which is why box 310 can't exceed box 300 minus box 305 (GOV.UK: Company Tax Return guide). A company that joins or leaves a group during a period has a shorter overlap, limited to the time both were in the same group.

How does the claim work with different year ends?

Each claim is limited to the overlap, so a loss can be split between two of the claimant's periods. In the example below the surrendering company's year ends three months after the claimant's, so about three quarters of its loss is claimable in the claimant's first year, and the rest in the next.

Brookfield Holdings Ltd and Brookfield Retail Ltd are fictional companies; Holdings owns all of Retail.

Holdings' available profits for the overlap are £73,000 × 275 ÷ 365 = £55,000. Retail's loss for the overlap is £36,500 × 275 ÷ 365 = £27,500. The lower figure, £27,500, is the most Holdings can claim for 2025, which leaves its taxable total profits at £45,500. The other £9,000 of Retail's loss falls in the 90 days from 1 January to 31 March 2026, so it can be claimed in Holdings' 2026 return instead, as long as Holdings has enough profits in that overlap. Retail's notice of consent must state the amount surrendered and its own accounting period, so it would give two notices, one for each claim (FA 1998 Sch 18 para 71).

How do you give consent to surrender a loss?

The surrendering company gives written notice of consent to the HMRC office that deals with its returns, at or before the time the claim is made. The claim must be accompanied by a copy of that notice, unless the group uses HMRC's simplified arrangements, where an authorised company signs for the group instead.

Without consent the claim is ineffective (FA 1998 Sch 18 para 70). The notice must give both companies' names, the amount surrendered, the surrendering company's accounting period and both companies' tax references, or it doesn't count either (para 71). A notice can't be amended, only withdrawn and replaced. Parts 2 and 4 of the CT600C can serve as the notice when the surrendering company completes them, and HMRC says the notice must reach the office handling the claimant's return on or before the day the claimant files it (GOV.UK: Completing the CT600C page). Under simplified arrangements, copies of each notice aren't needed: the claimant completes the claim authorisation section with the authorised company's name and the name and status of the person authorising (HMRC manual CTM97770).

Which CT600 and CT600C boxes do you fill in?

The claimant completes the CT600C and copies the totals to its CT600: current-period group relief from box C10 into box 310, and group relief for carried-forward losses from box C130 into box 312. A surrendering company completes the CT600C parts for amounts surrendered. HMRC's CT600C guidance sets out the four parts.

The CT600C can't cover more than 12 months, the same as the return it goes with (GOV.UK: Completing the CT600C page). Claims for carried-forward losses go only in Part 3 and their surrenders only in Part 4. For box 312, HMRC's return guide asks the computation to include a detailed calculation of the amount claimed, including the deductions allowance used (GOV.UK: Company Tax Return guide). Group relief for carried-forward losses also has an ordering rule: the claimant must first use its own carried-forward losses, and it counts against the £5 million deductions allowance, which our guide to trading losses brought forward explains.

When is the deadline for a group relief claim?

A claim can normally be made, or withdrawn, up to the first anniversary of the claimant's filing date, which is usually two years after the end of its accounting period. It can be later if HMRC is enquiring into the return or amending it, or if an HMRC officer allows a late claim.

FA 1998 Sch 18 para 74 sets the latest of four dates: the first anniversary of the filing date, 30 days after an enquiry into the return is completed, 30 days after HMRC amends the return following an enquiry, and 30 days after any appeal against that amendment is decided. Outside those dates, a claim needs an HMRC officer's agreement. The claim itself is made by including it in the claimant's return, either the original return or an amended one (para 67), which is why a group often finalises its losses after the first returns are filed and then amends. The filing date is normally 12 months after the end of the accounting period (GOV.UK: Company Tax Returns). A company that has already filed its CT600 can still add a group relief claim by amending it within the time limit; our guide to correcting a CT600 after filing covers amendments.

Can Taxley file a group relief claim on a CT600?

Yes, for UK companies in a 75% group. Taxley handles claims and surrenders of this period's losses, limits each claim to the company's available profits, works out the overlap limit where the two periods differ, takes the consent details, prints a notice of consent, and files the CT600C with the CT600. Some group cases it can't file yet, and it says so before you pay.

Taxley (taxley.co.uk), UK online software that prepares and files the Company Tax Return (CT600) with HMRC and the annual accounts with Companies House, has a Group relief section in the return. You add each claim, or each surrender of a trading loss, loan-relationship deficit or UK property loss. Where the two companies' periods differ, Taxley asks for the other company's total loss and any amounts already claimed, works out the overlap limit and flags a claim above it. Where the periods match, it limits the claim to the company's available profits, so check yourself that the surrendering company has enough unused loss. It asks how consent was given and warns about a claim made over a year after the filing date. It can't file yet: consortium relief or group relief with companies outside the UK, a return that both claims and surrenders, a period over 12 months, and a company that joined or left the group during the period. If the company is in a group, Taxley states a nil allowance. It files only when it can confirm the earlier losses used are no more than half the profits they're set against. Otherwise it tells you before you pay. Taxley can't file group returns using capital losses from earlier periods. Take the 30-second check to see whether Taxley fits your company.

Frequently asked questions

Can a company claim group relief from a sister company?

Yes, if both are 75% subsidiaries of the same parent company. Sister companies owned directly by the same individual aren't a group for this purpose, because the group test needs a parent company at the top that meets the share, profit and asset tests.

Does the surrendering company have to file its return first?

No. Consent must reach HMRC at or before the time the claim is made, but the surrendering company's own return can follow later. Its return must then show the same amount surrendered, so agree the figures between the companies before either files.

Can one return both claim and surrender group relief?

A company usually either claims, because it has profits, or surrenders, because it has a loss, for a given period. If one return needs both, check the limits on each carefully. Taxley can't file a return that both claims and surrenders for the same period yet.

Can losses be surrendered to a company outside the UK?

Generally no. Both companies must be UK related, which means UK resident or within the charge to UK Corporation Tax, for example through a UK permanent establishment. Special rules for some overseas losses are narrow and need specialist advice.

Is a payment for group relief taxable?

No, up to the amount of the loss surrendered. A payment from the claimant to the surrendering company for the relief, made under an agreement between them, is ignored for Corporation Tax in both companies. The companies agree the amount between themselves.

General information, not personalised tax or accounting advice.