Accounting technology / Glossary / Corporation tax software

What is corporation tax software?

Definition

Corporation tax software prepares a company's CT600 Company Tax Return, works out the tax computation and files both to HM Revenue and Customs with the accounts in iXBRL. Since the joint HM Revenue and Customs and Companies House filing service closed on 31 March 2026, UK companies and their accountants must use commercial software to file.

Also calledCT600 softwareCT600 filing software

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Return due: 12 months after period end
Tax due: 9 months and 1 day
Late filing: £200, then more

How corporation tax software works

A company must file a Company Tax Return within 12 months of the end of its accounting period, even when it makes a loss or has no tax to pay, and pay the tax nine months and one day after the period ends; companies with taxable profits over £1.5 million pay in instalments. The software takes the accounts, often from an accounts production module, builds the computation, completes the CT600 and attaches iXBRL-tagged accounts and computations. Paper returns are allowed only with a reasonable excuse or when filing in Welsh. HM Revenue and Customs's list of Corporation Tax software suppliers, updated in October 2026, has about 50 products that produce and submit the CT600. Practice products price by number of clients: TaxCalc Corporation Tax starts at £235 a year plus VAT for 12 clients and Capium at £20 a month plus VAT for up to 100. For a single company, Ftax starts at £11 plus VAT, Andica's CT600 costs £50 plus VAT on Windows, and Xero's company accounts and tax add-on costs £120 a year plus VAT. IRIS Keytime was discontinued on 31 March 2026, and IRIS points its users to IRIS Elements.

Common questions

Is there free corporation tax software?+

Not from HM Revenue and Customs any more: its joint filing service with Companies House closed on 31 March 2026. Xero Tax comes at no extra cost for UK Xero partners, and Ftax starts at £11 plus VAT for a small company.

What are the penalties for filing a CT600 late?+

£200 one day late and another £200 at three months. At six months HM Revenue and Customs estimates the bill and adds 10% of the unpaid tax, and another 10% at 12 months. After three late returns in a row the £200 penalties rise to £1,000 each.

What is CT600 bridging software?+

Bridging software files accounts and computations prepared elsewhere, such as in Excel. On HMRC's list these appear as iXBRL conversion software, which tags finished accounts so they can be sent with the CT600.

Which corporation tax software do accountants use?+

Practices use products that price by number of clients, such as TaxCalc, IRIS Elements Tax, Capium and Xero Tax, often alongside the same supplier's accounts production software.