Corporation tax returns for UK companies and accounting practices

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The CT600 and its computations, prepared from the finalised accounts so the two tie out first time. Marginal relief, associated companies and losses are worked through rather than estimated.

Figures checked against GOV.UK on 14 October 2026. General information, not advice.

Corporation tax for your company

What we do

Prepare the tax computation and the CT600 from your year-end accounts, and work out what's due and when.

What you get back

The return, the computation, and the payment amount and date, for you to approve.

Paying the tax

Due 9 months and 1 day after the end of the accounting period, for companies outside the quarterly instalment regime. The return itself is due 12 months after the period end.

Outsourced corporation tax preparation for accounting firms

How it works

We prepare the computation and CT600 alongside the accounts or from your finalised set, with a review note on judgement areas.

Filing

Prepared ready to file under your credentials, after your review.

Who does what is set out in full on our services page.

Corporation tax rates, financial year 2026

Small profits rate

19% on profits up to £50,000.

Main rate

25% on profits over £250,000.

Marginal relief

Applies between £50,000 and £250,000. The limits are divided by the number of associated companies. Try our corporation tax calculator.

Deadlines

Payment 9 months and 1 day after the period end. CT600 12 months after the period end.

Common questions

When is corporation tax due?

Payment is due 9 months and 1 day after the end of the accounting period for most small companies. The CT600 return is due 12 months after the period end.

What is the corporation tax rate for 2026?

19% on profits up to £50,000 and 25% over £250,000, with marginal relief between the two.

Can you prepare CT600s for my practice's clients?

Yes. We prepare the computation and return, and you review and file under your credentials.

Talk to us

Start with the one line that takes the most of your time. We scope it in a short call. Start a conversation.

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Statutory accounts · Company filings · Bookkeeping services · Company deadlines checker · First-year company accounts · All services