Corporation Tax
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The CT600 Series
The CT600 series is HMRC’s set of Corporation Tax return forms. The main CT600 is the self-assessment Company Tax Return, in which a UK limited company declares its profits, calculates its Corporation Tax and shows whether tax is still due or a repayment is owed; it is normally filed online with accounts and computations in iXBRL format. Supplementary pages are added where needed: CT600A for close company loans to participators (section 455 tax, charged at 35.75% on loans made after 6 April 2026), CT600B for controlled foreign companies, foreign permanent establishment exemptions and hybrid mismatches, CT600C for group and consortium relief, CT600D for insurers with overseas life assurance business, and CT600E for charities and Community Amateur Sports Clubs. The return is due within 12 months of the end of the accounting period, while the Corporation Tax itself is normally payable 9 months and 1 day after the period end. The CT600 (Short) 2008 is a withdrawn historic form, so the current CT600 should be used instead.
CT600 Company Tax Return (2026, Version 3)
Purpose
The CT600 is the main Company Tax Return used by a UK limited company to tell HMRC how much profit it made in an accounting period and how much Corporation Tax it owes. It is a self-assessment form, which means the company itself works out its income, gains, deductions and reliefs, calculates the tax, and declares the result to HMRC. The form also tells HMRC whether tax is still outstanding or whether the company has overpaid and is due a repayment.
Deadlines
The return must be filed within 12 months of the end of the accounting period. The Corporation Tax itself must normally be paid within 9 months and 1 day of the end of the period. Large companies (profits above £1.5 million, divided by the number of associated companies) pay by quarterly instalments, and very large companies (profits above £20 million) pay their instalments earlier. A late return incurs an automatic £100 The A filed return can generally be amended within 12 months of the filing deadline.
Requirements
To complete the CT600 the company needs its Corporation Tax UTR and Companies House number, the exact accounting period dates, and the Government Gateway login with the company's authentication code. It must have approved statutory accounts and a tax computation, both in iXBRL format, plus bookkeeping records that support turnover, expenses, capital allowances pools, loss records, bank interest, property income, chargeable gains and dividends. The company must also know the number of associated companies in the period, details of any group relationships, the amount of tax already paid, and the details of any claims being made, for example R&D relief, group relief or double taxation relief.
Filing Process
The form starts with the company information section. Enter the company name (box 1), Companies House registration number (box 2), the 10-digit Unique Taxpayer Reference (box 3) and the type of company (box 4). In boxes 30 and 35 enter the start and end dates of the accounting period; the period covered cannot be longer than 12 months. Then tick the "About this return" boxes that apply, such as a repayment being due, estimated figures being used, the company being part of a large group, or transfer pricing claims. In boxes 80 to 90 confirm that accounts and computations are attached, and in boxes 95 to 144 tick every supplementary page that is enclosed. The Income section begins with box 145, Total turnover from trade. This is the revenue figure and it is mandatory for trading companies: it is the total sales or fees invoiced by the company in the period. In box 155 enter the trading profit. In practice the return is submitted online with accounts and computations in iXBRL format, so the commercial software or HMRC's online service fills many of these boxes automatically from the computation.
CT600A Close Company Loans and Arrangements to Confer Benefits on Participators (2026, Version 3)
Purpose
CT600A is a supplementary page to the CT600. It is used by a close company (generally a company controlled by five or fewer shareholders or by its directors) that has lent money to, or arranged to give a benefit to, a participator (a shareholder or director) or an associate such as a relative. The page works out the extra tax charge, under section 455 of the Corporation Tax Act 2010, which the company must pay on such loans if they are still outstanding nine months after the end of the accounting period.
Deadlines
Section 455 tax is due 9 months and 1 day after the end of the accounting period in which the loan was made. The CT600A is filed with the CT600, normally within 12 months of the period end.
Requirements
The company must have a full loan account or director's loan account ledger showing every advance, repayment, write-off and release during the period and the dates on which they happened. It needs the names of all participators and associates who received loans or benefits, the balance outstanding at period end, and evidence of any repayments, board minutes or dividends used to clear the loans. The company must also know the section 455 rate that applies to the loans (33.75 per cent for loans made before 6 April 2026; the rate has been increased from 33.75% to 35.75% per cent for loans after 6 April 2026).
Filing Process
Start with the company information section: company name (A1), tax reference (A2) and the period covered by the page (A3 and A4), which cannot be longer than 12 months. Then complete Part 1, "Loans and arrangements made during the return period", in box A10. For each participator or associate (up to six rows) enter their name in column A and the amount of the loan or benefit in column B. The total goes in box A15, and box A20 shows the tax chargeable, which is box A15 multiplied by the applicable rate. Put an X in the box provided if any of the loans were repaid, released or written off before the end of the period. Part 2 gives relief for amounts repaid, released or written off within nine months of the end of the period. In box A25, for each person, enter the name, the amount repaid, the amount released or written off, and the date of the repayment or write-off. The totals go in boxes A30 and A35, the combined total in box A40, and the relief due in box A45, which is box A40 multiplied by the rate. Copy the figure in box A80 to box 480 on the CT600 so that it becomes part of the tax chargeable.
CT600B Controlled Foreign Companies, Foreign Permanent Establishment Exemptions, Hybrid and Other Mismatches (2022, Version 3)
Purpose
CT600B is a supplementary page to the CT600 for companies with overseas interests. It is used to report any Controlled Foreign Company (CFC) charge, which is a UK tax charge on profits of low-taxed overseas companies that are controlled by UK residents, and to claim the foreign permanent establishment exemption for overseas branches. It also collects information about hybrid and other mismatch arrangements, where the tax treatment of a financial instrument, entity or payment differs between countries and.
Deadlines
File the page with the CT600 within 12 months of the accounting period end. Any CFC charge is payable 9 months and 1 day after the period end. A foreign permanent establishment exemption election must be made before the start of the relevant accounting period.
Requirements
Provide details of the overseas companies or branches, including accounts, tax computations, ownership/control, and local tax paid. Identify applicable CFC rules, gateway tests, and exemptions, with supporting workings for any foreign permanent establishment exemption. For mismatch provisions, provide details of group financing, hybrid arrangements, and counteraction calculations.
Filing Process
Complete the company information section first, with the company name (B1), tax reference (B2) and the period covered (B3 and B4). In the CFC and foreign permanent establishment table (box B5) there is one row for each CFC, with up to twelve rows. For each CFC enter its name, the territory of residence, and the type of exemption due if any, and the percentage of apportionable profits and creditable tax that relates to the UK company (column D). Then complete the chargeable profits (column E), the tax on those chargeable profits (F), creditable tax (G), reliefs in terms of tax (H), restricted ACT (I) and the resulting CFC charge due (J). The totals of the columns are entered on the Total row, and the total CFC charge due must be entered in box 490 on the CT600. Box B35 should be ticked if this is the first period in which an election for the foreign permanent establishment exemption applies. The Hybrid and other mismatches section requires an X in the relevant boxes: B40 if the company is a hybrid entity, B45 if there were transactions with hybrid entities in the same control group, B50 for hybrid or impermissible deduction or non-inclusion mismatches involving a financial instrument, B55 for an excessive permanent establishment deduction, B60 for a multinational payee mismatch and B65 if there has been a counteraction under Part 6A of TIOPA 2010. If a counteraction applies, enter the total counteraction in B70, the section 259LA deduction in B75, and the dual inclusion income (DII) surplus allocation claims in B80 and B85.
CT600C Group and Consortium Relief (2018, Version 3)
Purpose
CT600C is a supplementary page for companies that belong to a group or a consortium and want to claim or surrender losses and other reliefs between companies, so that one company's loss reduces another company's profits. The claiming company uses it to show how much relief it is taking in its own return and from which companies, and the surrendering company uses it to show how much relief it is giving away and to whom. For this reason it can also be used as the formal notice of consent to the surrender.
Deadlines
File the page with the CT600 within 12 months after the accounting period ends. A group relief claim is normally due within 1 year of the claimant company’s filing date. Corporation Tax is payable 9 months and 1 day after the period end.
Requirements
The group structure must be established first: companies must be in a 75 per cent group relationship (or be members of a consortium) throughout the overlapping period. The company needs the tax computations of both the surrendering and the claimant company, the exact amount of surrenderable losses available, the accounting periods which overlap, and the UTR of each company. A notice of consent from every surrendering company must be attached to the claim unless a simplified arrangement is in force, and consortium claims need the consent of all consortium members.
Filing Process
Begin with the company information section (C1 to C4: name, tax reference and period). Part 1 is completed by the claimant company that wants group relief in its calculation. In box C5, list each surrendering company in up to seven rows with its name, its accounting period if different from this return, its 10-digit tax reference (or the company registration number if the UTR is not known), and the amount claimed. The total in box C10 must be entered in box 310 of the CT600. Put an X in box C15 or C20 if the claim involves a non-resident company or a UK permanent establishment of a non-resident company. If a simplified arrangement is in force and copies of consent are not attached, tick box C25 and complete C30 to C40 with the name of the authorised company, the person authorising and their status. Part 2 is completed by the surrendering company. In boxes C45 to C75 it splits the amount surrendered between trading losses (including Northern Ireland trading losses), excess non-trade capital allowances, non-trading loan relationship deficits, excess qualifying charitable donations, excess UK property business losses, excess management expenses and non-trading intangible fixed asset deficits, and the total goes in C80. The claimant company completes box C125 and the total in C130 goes to box 312 of the CT600, and the surrendering company completes boxes C160 to C185 and C190 to C225.
CT600D Insurance (2015, Version 3)
Purpose
CT600D is a supplementary page for insurance companies carrying on overseas life assurance business. It confirms that the required certificates, documents, undertakings and declarations have been obtained and completed under the relevant regulations, allowing qualifying policies and contracts to be treated as overseas life assurance business.
Deadlines
CT600D is filed with the CT600 within 12 months of the end of the accounting period. Corporation Tax is payable 9 months and 1 day after the period end. The required declarations should be held when the policies are entered into.
Requirements
The company must be a life insurance company with overseas life assurance business. It needs a complete file of certificates, declarations and undertakings from its policyholders showing that they are non-UK residents, as required by the 1995 Regulations, and it must be able to produce them if HMRC asks. It also needs the full tax computation for the insurance business and the regulatory returns that support the figures in the CT600.
Filing Process
The page is simple. Enter the company name (D1), tax reference (D2) and the period covered by the page (D3 and D4), which cannot exceed 12 months. Then, only if the company has done everything required by the compliance regulations for policies and contracts entered into in the accounting period, put an X in box D5. If the company has not completed the necessary certificates, declarations and undertakings, box D5 must be left blank and the company should take advice, since the business cannot then be treated as overseas life assurance business. The page is then tick-boxed as an enclosure on the CT600 (box 110) and submitted with the return. Other insurance information, for example life assurance company tax credit, is entered on the main CT600 form itself.
CT600E Charities and Community Amateur Sports Clubs (2026, Version 3)
Purpose
CT600E is a supplementary page for charities and Community Amateur Sports Clubs (CASCs). It is used to claim Corporation Tax exemptions on income and gains applied for charitable purposes, provide HMRC with details of income, expenditure and assets, and claim repayment of tax deducted or overpaid.
Deadlines
A charity must file a Company Tax Return within 12 months after the accounting period ends if HMRC requires one. If it has taxable non-exempt income or gains above the relevant threshold, it must notify HMRC within 3 months of the period end.
Requirements
The charity must be recognised by HMRC as a charity (or a registered CASC) and have its HMRC charity reference. It needs its approved annual accounts, a detailed breakdown of income by source and of expenditure by type, a record of asset purchases and disposals, a register of legacies received, and details of any trading subsidiaries. It also needs evidence that all of its income has been applied for charitable purposes only, because the exemption can be lost on any expenditure that is not charitable.
Filing Process
Fill in the company information section first: the name of the charity or CASC (E1), the tax reference (E2) and the period (E3 and E4). In "Claims to exemption", which must always be completed, enter the Charity/CASC repayment reference (E5) and the Charity Commission or OSCR registration number (E10). Put an X in E15 if the charity is claiming exemption (also if it had no income or gains), an X in E20 if all income and gains are exempt and have been or will be applied for charitable purposes only, or an X in E25 if some income may not be exempt, in which case the CT600 must also be completed. Finally the authorised person enters their name (E30), status (E35) and the date (E40) to make the claim. The Information required section asks for amounts as shown in the charity's accounts. Income is split into exempt trading turnover (E50), investment income (E55), UK land and buildings (E60), Gift Aid (E65), income from other charities (E70), gifts of shares (E75), gifts of real property (E80), other sources (E85) and legacy income (E88), with the total in E90. Expenditure is shown in boxes E95 to E120, covering trading costs, property costs, administration and governance, grants and donations in the UK and overseas, and other costs, and the total goes in E125. Box E45 is ticked if tax has been over-claimed. Repayment claims are made through the HMRC Charities Online service, not on the paper form.
CT600 (Short) 2008 Company Short Tax Return (2008, Version 2) - Historic Form
Purpose
The CT600 (Short) was a shortened, simplified version of the Company Tax Return, designed for small and simple companies with straightforward affairs for accounting periods ending on or after 1 July 1999. It collected the same core information as the full CT600: turnover, trading and other profits, deductions and the Corporation Tax payable. The uploaded edition (September 2008, Version 2) refers to old-law concepts such as Case I trading losses, S75 ICTA 1988 management expenses, charges paid, the starting.
Deadlines
When the form was in use the return was due 12 months after the end of the accounting period and the tax was due nine months and one day after the end of the period, the same dates that apply now. A £100 Because the form is withdrawn, a company with any current or recent accounting period should file the current CT600 instead.
Requirements
The company needed its accounts and computations, its UTR and registration number, the CT603 notice to deliver, and records to support the turnover, expenses, capital allowances and tax already paid. The form could only be used by companies that met the conditions on pages 3 to 6 of the old Company Tax Return Guide; companies with complicated affairs, large companies or those with items not covered had to use the full CT600.
Filing Process
Page 1 starts with the company name, company registration number, tax reference as shown on the CT603 notice, the type of company and the registered office address. In "About this return" enter the period, tick the boxes that apply (repayment due, estimated figures, group that is not small, tax avoidance scheme notice, transfer pricing), say whether accounts and computations are attached and tick the supplementary pages enclosed (CT600A, CT600E, CT600J). Page 2 is the tax calculation. Box 1 is the total turnover from the trade or profession (the mandatory revenue figure). Box 3 is the trading and professional profit, which is revenue less allowable expenses and after tax adjustments, box 4 is losses brought forward, and box 5 is the net trading profit. Then add interest (box 6), income from UK land and buildings (box 11), annual profits (box 14) and net chargeable gains (boxes 16 to 18) to arrive at box 21, profits before other deductions and reliefs. Deduct management expenses (24), trading losses (30), non-trade capital allowances (32) and charges paid (35) to arrive at box 37, profits chargeable to Corporation Tax. Boxes 38 to 70 deal with franked investment income, associated companies, rates of tax, marginal relief and the tax chargeable. Page 4 contains the repayment request, bank details, the authority to pay a nominee and the declaration signed by an authorised officer.