CT600Filing - 2026 Pricing, Features, Reviews & Alternatives

CT600Filing is an HMRC-recognised online platform for preparing and submitting CT600 Corporation Tax returns, built for UK limited companies, sole directors, contractors, and accountancy practices.

Since HMRC closed its free CATO joint filing service, small companies have needed an affordable commercial route to stay compliant. CT600Filing replaces what CATO did — the return, the accounts, and both government submissions — in one guided online process.

KEY CAPABILITIES

- Guided, box-by-box CT600 preparation with the tax calculation built in — no tax software experience needed

- Automatic generation of FRS-102 and FRS-105 iXBRL company accounts in the format HMRC requires

- Direct electronic submission to HMRC and to the Companies House XML Gateway from one account

- Marginal Relief and small profits rate handled in the calculation

- Suitable for straightforward trading companies, dormant companies, and property SPVs

- Agent-friendly: accountants can prepare and file on behalf of clients

PRICING

Pay-per-filing from £49 + VAT — no monthly or annual subscriptions. Prepare your return free of charge and pay only when you submit. Every filing fee includes unlimited amendments and re-submissions for that accounting period.

WHO IT'S FOR

UK limited companies filing their own Corporation Tax returns — small businesses, contractors, and directors — plus accountants and agents filing for clients.

CT600Filing is operated by Swift Catalyst Ltd, a UK company specialising in HMRC-recognised tax filing software. Everything runs in the browser — no installation required.