CT600C: group and consortium relief, box by box

Companies in the same group can share their losses. A loss-making company can surrender its loss to a profitable fellow member, which claims it as group relief and pays less Corporation Tax. The same can happen between a consortium-owned company and its members, as consortium relief. Both are reported on CT600C, the group and consortium relief supplementary page of the Company Tax Return. This guide explains when you need a CT600C, how claims and surrenders work, how to complete the page in Tax Optimiser, and what every box from C1 to C225 means.

When a company needs a CT600C

File a CT600C, and tick box 105 on the CT600, if in the return period the company:

• claims group or consortium relief for another company’s losses of the same period (Part 1, which feeds box 310);
• surrenders any of its own losses of the period to another company (Part 2);
• claims group relief for carried-forward losses of another company (Part 3, which feeds box 312); or
• surrenders carried-forward losses to another company (Part 4).

Both sides file: the claimant on its own return, and the surrendering company on its own return. A company that claims and surrenders in the same period completes more than one part of the same page.

Group relief and consortium relief in plain English

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

A consortium company is one that is at least 75% owned by companies that each hold at least 5% and none of which holds 75% or more on its own. Losses can move between the consortium company and its members, but only in proportion to each member’s interest, and every other member has to consent.

A few rules shape every claim:

• Only overlapping periods count. If the two companies’ accounting periods don’t match, the loss and the profit are both apportioned to the part of the periods that overlap.
• The claimant can only use its own profits. Group relief is deducted after every other relief, including qualifying charitable donations, so it can never create a loss for the claimant.
• What can be surrendered depends on the type of loss. Trading losses, excess capital allowances and non-trading loan relationship deficits can be surrendered whether or not the surrendering company could use them itself. UK property losses, management expenses, qualifying donations and non-trading deficits on intangible fixed assets can only be surrendered to the extent they exceed the company’s own profits.
• Carried-forward losses that arose on or after 1 April 2017 can also be surrendered (Part 5A of the Corporation Tax Act 2010). The claimant’s use of them counts towards its £5 million deductions allowance, shared across the group.
• Consent is needed. Every claim needs the surrendering company’s consent, given either on a notice of consent or on the surrendering company’s own CT600C. Groups that file often agree a simplified arrangement with HMRC, under which one nominated company authorises claims for the whole group.

Group companies are also associated companies for the small profits rate and marginal relief, so a claimant in a group usually has lower thresholds than a stand-alone company. Record them on the General tab (box 326).

How the relief works on the return

On the claimant’s CT600, profits chargeable to Corporation Tax are worked out as box 300 less qualifying donations (box 305), less group relief (box 310), less group relief for carried-forward losses (box 312). HMRC requires box 310 to equal the total claimed on the CT600C (C10) and box 312 to equal C130 exactly, and neither can be more than the profits left after every other relief.

Worked example — claiming. A company has £150,000 of profits. It claims £40,000 of a subsidiary’s trading loss and £10,000 from a consortium company, a total of £50,000 in box 310. It also claims £20,000 of another group member’s carried-forward losses in box 312. Its profits chargeable to Corporation Tax fall to £80,000.

Worked example — surrendering. Another company makes a £30,000 trading loss and has £20,000 of losses brought forward. It surrenders £25,000 of this year’s loss to a profitable sister company (C45) and £15,000 of the brought-forward loss to its parent (C160). Only £10,000 is left to carry forward. Box 780, the loss arising in the period, still shows the full £30,000.

Completing the CT600C in Tax Optimiser

Open the period’s Corporation Tax workspace and choose Group Relief in the Sections menu (if it is not listed, click Add Section at the bottom of the menu, tick it and click Save). The page has four tabs, one for each part of the form. If the period of account is longer than 12 months it is filed as two returns, each with its own CT600C; use the Return 1 and Return 2 buttons to switch between them.

Step 1 — Enter the claims (Parts 1 and 3)

On Part 1 — claims, click Add company for each surrendering company and enter its name, its tax reference and the amount claimed. Enter the company’s accounting period only if it is different from yours. The tax reference is the 10-digit UTR; if you don’t have it, enter the company registration number instead, as HMRC allows.

The total (C10) is shown underneath, together with the profits available for this claim. If the claim is more than the profits left after every other relief, the figure turns red and the return can’t be filed until you reduce it. Tax Optimiser won’t quietly trim it, because box 310 has to equal C10.

Tick C15 or C20 if the losses come from a non-resident company. Group relief isn’t available for losses of a non-resident company (other than a UK permanent establishment) for periods starting on or after 27 October 2021, and Tax Optimiser blocks C20 for those periods.

Part 3 — c/f loss claims works the same way for carried-forward losses. Its total (C130) goes to box 312 and can only use the profits left after box 310.

Step 2 — Authorise the claims

Each claim part has a claim authorisation block: tick the box and enter the authorised company, the person authorising and their status. The tick tells HMRC that the claim is authorised under a simplified arrangement, so use it only if the group already has one. A simplified arrangement is not automatic: the group has to apply to HMRC for one in writing, and it must be in force when the claim is made. Without one, HMRC requires a copy of each surrendering company’s notice of consent to be attached to the claim. Online returns filed through Tax Optimiser can’t carry those copies. That is a limit of Tax Optimiser, not a filing rule: a group relief claim can be filed from Tax Optimiser only where a simplified arrangement is in force.

Step 3 — Enter the surrenders (Parts 2 and 4)

On Part 2 — surrenders, enter the amount surrendered for each type of loss (C45 to C75). Next to the trading loss, the loan relationship deficit and the property loss, Tax Optimiser shows how much is available to surrender. Then add each claimant company and the amount it receives. The claimant amounts (C90) must add up to the total surrendered (C80); a warning appears if they don’t.

The details of company surrendering relief make this return the notice of consent. The company name, tax reference and accounting period are copied from the return. The person authorising and their status default to the director signing the CT600; enter different ones if someone else is authorised. Tick A simplified arrangement is in force if one applies.

Part 4 — c/f loss surrenders works the same way for losses brought forward into the period. Part 2 can only surrender this period’s trading loss; a brought-forward trading loss must go in Part 4 (C160).

Step 4 — Save and check the return

Click Save. As soon as any part has an entry, Tax Optimiser:

• ticks box 105 and fills boxes 310 and 312 from the claims, reducing profits chargeable and the tax;
• takes the surrendered trading losses, UK property losses and loan relationship deficits off the amounts carried forward, and shows each surrender on the Losses section;
• adds “Group relief claimed” lines to the profits chargeable page of the computation, a “Loss surrendered as group relief” line to the losses page, and a Group and consortium relief page listing every claim and surrender;
• lists the completed form under Supplementary pages on the CT600 Document tab, where you can view or download it. Tables with more rows than the printed form has room for continue on an extra page at the end.

What Tax Optimiser checks, and what it does not do

Before filing, Tax Optimiser checks what HMRC’s validation rejects: a company name that is missing or longer than 56 characters; a tax reference that isn’t 8 to 20 letters and digits; a claim with no amount; another company’s accounting period that is longer than 12 months or doesn’t overlap the return; a claim with no authorisation; claimant amounts that don’t add up to the total surrendered; a claim larger than the profits available; and a surrender larger than the loss available.

What it does not do is decide whether the relief is due. It doesn’t test the 75% group or consortium conditions, apportion losses and profits to overlapping periods, work out a consortium member’s share, check the other company’s return, or apply the £5 million deductions allowance to carried-forward loss claims. Those figures come from the group’s own working papers. Surrenders of excess capital allowances, qualifying donations, management expenses and intangible fixed asset deficits are reported on the CT600C but not tracked in the carry-forward, because Tax Optimiser doesn’t hold those amounts separately.

CT600C box by box

Box C1 — Company name

The company’s registered name, as on the CT600.

Box C2 — Tax reference

The company’s 10-digit Unique Taxpayer Reference (UTR).

Boxes C3 and C4 — Period covered by this supplementary page

The start and end dates of the return period. It cannot exceed 12 months, so a long period of account has a CT600C for each return.

Box C5 — Claims to group relief

One row per surrendering company whose current-period losses the company claims. Include consortium claims. Column A is the name of the surrendering company; column B its accounting period, only if different from the period covered by this return; column C its tax reference (the 10-digit UTR, or something else that identifies it, such as its registration number); and column D the amount claimed.

Box C10 — Total amount claimed

The total of column D. Enter it in box 310 of the CT600; HMRC checks that the two are equal.

Box C15 — Losses of a UK permanent establishment of a non-resident company

Put an X if a claim involves losses of a trade carried on in the UK through a permanent establishment by a non-resident company.

Box C20 — Losses of other non-resident companies

Put an X if a claim involves losses of a non-resident company not covered by C15, or a non-resident link company. Not available for accounting periods starting on or after 27 October 2021; a period that straddles that date is split into two.

Box C25 — Claim authorisation

Put an X to confirm the claim has been authorised under a simplified arrangement, where copies of the notices of consent are not supplied.

Box C30 — Name of authorised company

The company authorised to act for the companies within the simplified arrangement.

Box C35 — Full name of person authorising

Any person authorised to act on behalf of that company.

Box C40 — Status

The authorising person’s status, for example Director.

Box C45 — Trading losses, total

The trading losses of the period surrendered as group relief.

Box C46 — Trading losses, Northern Ireland

HMRC’s guidance is to leave this box blank.

Box C50 — Excess non-trade capital allowances

Non-trade capital allowances surrendered: the excess over the income from which they are primarily deductible.

Box C55 — Non-trading deficit on loan relationships

The non-trading loan relationship deficit of the period surrendered.

Box C60 — Excess qualifying charitable donations

Charitable and grassroots sport donations surrendered: the excess over the company’s profits.

Box C65 — Excess UK property business losses

UK property business losses surrendered: the excess over the company’s profits.

Box C70 — Excess management expenses

Management expenses surrendered: the excess over the company’s profits.

Box C75 — Non-trading deficits on intangible fixed assets

The non-trading deficit on intangible fixed assets surrendered.

Box C80 — Total surrendered

The total of boxes C45 to C75.

Box C85 — Details of surrender

One row per claimant company: its name, its accounting period if different from this return’s, its tax reference and the amount surrendered to it.

Box C90 — Total amount surrendered

The total of the C85 amounts. It must equal C80.

Boxes C95 to C120 — Details of company surrendering relief

Complete all of these to use the CT600C as the notice of consent to surrender: the company name (C95), tax reference (C100) and accounting period (C105 and C110), which must match the CT600, then the full name (C115) and status (C120) of the person authorising. Except where a liquidator or administrator has been appointed, anyone authorised to do so can sign on the company’s behalf.

Box C125 — Claims to group relief for carried-forward losses

As C5, for carried-forward losses claimed from other group companies.

Box C130 — Total amount claimed

The total of the C125 amounts. Enter it in box 312 of the CT600; HMRC checks that the two are equal.

Box C135 — Losses of a UK permanent establishment of a non-resident company

Put an X if a carried-forward loss claim involves losses of a trade carried on in the UK through a permanent establishment by a non-resident company.

Boxes C140 to C155 — Claim authorisation

As C25 to C40, for the Part 3 claims.

Box C160 — Trading losses carried forward, total

Carried-forward trading losses surrendered.

Box C161 — Trading losses carried forward, Northern Ireland

HMRC’s guidance is to leave this box blank.

Box C165 — Non-trading deficit on loan relationships carried forward

Carried-forward loan relationship deficits surrendered.

Box C170 — UK property business losses carried forward

Carried-forward UK property business losses surrendered.

Box C175 — Management expenses carried forward

Carried-forward management expenses surrendered.

Box C180 — Non-trading deficits on intangible fixed assets carried forward

Carried-forward intangible fixed asset deficits surrendered.

Box C185 — Total surrendered

The total of boxes C160 to C180.

Boxes C190 and C195 — Details of surrender

As C85 and C90, for the carried-forward losses surrendered. C195 must equal C185.

Boxes C200 to C225 — Details of company surrendering relief

As C95 to C120, making the CT600C the notice of consent for the Part 4 surrenders.

Main return: boxes 105, 310 and 312

Box 105 is ticked when the CT600C is attached. Box 310, group relief, equals C10, and box 312, group relief for carried-forward losses, equals C130. Tax Optimiser sets all three from the CT600C, and HMRC rejects a return with box 310 or 312 but no CT600C.

Common questions

Where to go next

• Corporation Tax in Tax Optimiser — the full journey from trial balance to filed return.
• CT600 box-by-box guide — every box on the main return.
• HMRC’s CT600C guidance — the official notes for every box.
• HMRC’s Company Taxation Manual — group relief (CTM80100 onwards).