Corporation Tax glossary

Tax relief that lets a business deduct some or all of the value of items it keeps to use in the business — such as equipment, machinery and business vehicles — from its profits before tax. A limited company claims them in its Company Tax Return, with a separate capital allowances calculation.

Source: GOV.UK: Claim capital allowances · GOV.UK: How to claim capital allowances | Guide: Company equipment: expense or capital allowance?

The form HMRC sends a newly incorporated company when it sets the company up for Corporation Tax. It gives the company's Unique Taxpayer Reference (UTR) and explains how to give HMRC any registration details it still needs.

Source: HMRC manual COM40030 | Guide: What is a UTR and where do I find it?

HMRC's Company Tax Return form, used to report a company's taxable profits and the Corporation Tax due for an accounting period. It is filed online, with the company's accounts and tax computations in iXBRL format.

Source: GOV.UK: Company Tax Return (CT600) · GOV.UK: XBRL guide for UK businesses | Guide: What is a CT600 and how do you file one?

HMRC's "notice to deliver a Company Tax Return" — the formal notice requiring a company to file a return for a stated period. A company must file a return if it gets one; HMRC does not issue one to a company its records show as dormant.

Source: HMRC manual COM130130 · GOV.UK: Company Tax Returns | Guide: What is a UTR and where do I find it?

HMRC's own figure for the Corporation Tax it thinks a company owes, sent when the Company Tax Return is 6 months late. You cannot appeal against it: you need to pay the tax due and file the return, and HMRC then recalculates the interest and penalties.

Source: GOV.UK: Penalties for late filing | Guide: What happens if you file your CT600 late?

For Corporation Tax, a company is usually dormant if it is not doing business — trading includes buying, selling, renting property, advertising, employing someone or getting interest — and has no other income. Once HMRC knows, it need not file Company Tax Returns unless it gets a notice to deliver one, but it must still file accounts and confirmation statements at Companies House.

Source: GOV.UK: Dormant for Corporation Tax | Guide: How to file a dormant company tax return

The year Corporation Tax rates are set for. It starts on 1 April and is named after the calendar year it starts in, so financial year 2026 runs from 1 April 2026 to 31 March 2027. It is not the same as your company's own financial year.

Source: GOV.UK: Rates and allowances for Corporation Tax | Guide: Corporation Tax rates and marginal relief 2026/27

The small-entities section of FRS 102, the main UK accounting standard. A small company that chooses the small companies regime follows FRS 102's recognition and measurement rules, with reduced presentation and disclosure requirements.

Source: FRC: FRS 102 | Guide: FRS 105 vs FRS 102 §1A: which accounts to file

The accounting standard for the micro-entities regime. Using the regime is optional, but a micro-entity that chooses to prepare its accounts under it must apply FRS 105.

Source: FRC: FRS 105 | Guide: FRS 105 vs FRS 102 §1A: which accounts to file

The sign-in (a user ID of up to 12 characters and a password) for HMRC online services, including a business tax account. To file a company's return online, you use Government Gateway details with Corporation Tax added to the business tax account.

Source: GOV.UK: Sign in to HMRC online services · GOV.UK: Add Corporation Tax to your business tax account | Guide: How to file a CT600 yourself (without an accountant)

A human-readable report — effectively a web page — with machine-readable XBRL tags embedded in it. Companies must send the accounts and tax computations that go with their Company Tax Return in iXBRL.

Source: GOV.UK: XBRL guide for UK businesses | Guide: iXBRL accounts for a CT600: what to check beyond the PDF

The 25% Corporation Tax rate, paid when a company's profits are over £250,000 (financial year 2026). The limit is reduced for accounting periods shorter than 12 months and divided between associated companies.

Source: GOV.UK: Corporation Tax rates | Guide: Corporation Tax rates and marginal relief 2026/27

Relief that gives a gradual increase in the Corporation Tax rate between the 19% small profits rate and the 25% main rate, for profits between £50,000 and £250,000. Close investment-holding companies cannot claim it.

Source: GOV.UK: Marginal Relief for Corporation Tax | Guide: Corporation Tax rates and marginal relief 2026/27

A very small company that meets at least two of these: turnover of £1 million or less, £500,000 or less on its balance sheet, 10 employees or less. It can prepare simpler accounts and send Companies House only a balance sheet with less information.

Source: GOV.UK: Micro-entities, small and dormant companies | Guide: FRS 105 vs FRS 102 §1A: which accounts to file

Credits and debits on a company's loans and other money debts that are not part of its trade — for example interest on borrowing that is not used for trading. They are taxed or relieved separately from trading profits; net debits make a non-trading deficit, which can be set against other profits of the period, carried back 12 months against non-trading profits, or carried forward.

Source: HMRC manual CFM32030 | Guide: Corporation Tax for a property (rental) company

The period a company prepares its accounts for. It is usually 12 months but can be shorter, or up to 18 months if the year end is extended; a period of account longer than 12 months is split into two accounting periods, with two Company Tax Returns.

Source: HMRC manual CTM01405 · GOV.UK: Change your company's year end · GOV.UK: Accounting periods for Corporation Tax | Guide: First company accounts: why you may need two CT600s

The 19% Corporation Tax rate for companies with profits of £50,000 or less (financial year 2026). The £50,000 limit is reduced for accounting periods shorter than 12 months and divided between associated companies.

Source: GOV.UK: Corporation Tax rates | Guide: Corporation Tax rates and marginal relief 2026/27

The full annual accounts a private limited company must prepare from its company records at the end of its financial year. They are sent to both Companies House and HMRC, and are used to work out how much Corporation Tax to pay.

Source: GOV.UK: Prepare and file annual accounts | Guide: CT600, annual accounts or confirmation statement?

A loss made by the company's trade, worked out by making the usual tax adjustments to the loss in its accounts. It can be set against other profits of the same accounting period, carried back against profits of the previous 12 months, or carried forward — carried-forward relief is restricted to, broadly, a £5 million allowance plus 50% of remaining trading profits.

Source: GOV.UK: Calculating and claiming a loss | Guide: Company made a loss? Your CT600 still needs a loss schedule

The 10-digit number HMRC uses to identify a company for Corporation Tax. You can find it on any letter from HMRC about the company, and you need it to add Corporation Tax to the company's business tax account.

Source: GOV.UK: Find a lost UTR number · GOV.UK: Add Corporation Tax to your business tax account | Guide: What is a UTR and where do I find it?