HMRC Free CT600 Filing Closed: What UK Companies Must Do After April 2026

The free joint online service to file company accounts and Company Tax Returns with Companies House and HMRC closed on 31 March 2026. GOV.UK guidance updated on 1 April 2026 explains how companies that previously used that service should file going forward.

From 1 April 2026, you must use HMRC-recognised commercial software to file a Company Tax Return (CT600, computations, and accounts elements as required). Companies House accounts can still be filed by software, Companies House web services, or paper — but Corporation Tax returns for most companies must be filed online via software unless you have a reasonable excuse or are filing in Welsh on paper.

Companies House and HMRC stated the joint service was outdated: it no longer aligned with modern digital standards, enhanced corporation tax requirements, or company-law changes under the Economic Crime and Corporate Transparency Act. Closing it also supports wider Companies House reforms, including identity verification.

HMRC had already warned small unrepresented companies to download and retain prior returns before the portal switched off — historical CATO submissions are no longer available through that service. If you did not archive filings, reconstruct records from your own books, accountant copies, or Companies House filings where possible.

Choose commercial software that can produce the CT600 elements you need — return, tax computation, and iXBRL accounts where applicable — and that is listed among HMRC’s recognised Corporation Tax software suppliers. Agents can file on your behalf. Amendments or re-filing of rejected returns can use commercial software, a paper return to the Corporation Tax office, or an agent.

Deadlines are unchanged: the Company Tax Return is generally due 12 months after the end of the accounting period, and corporation tax is usually payable nine months and one day after the period end (instalment rules may apply for larger companies). Late filing still attracts automatic penalties — software choice does not alter those dates.

Charities, community amateur sports clubs, and flat management companies may still explore Corporation Tax filing exemptions when dormant, but Companies House accounts duties usually continue.

Confirm who will file the next CT600 (director via software, or your accountant). Diarise return and payment dates for every company you control. Keep digital books reconciled so software import or agent handover is clean. If incorporation no longer suits a tiny lifestyle business, GOV.UK also flags disincorporation as a structural option — take regulated advice before changing entity type.

FinnAccountings helps UK and Ireland limited companies organise bookkeeping and tax prep drafts with Chartered Accountant insight before you or your ICAEW/ACCA adviser files the CT600 through recognised software — start a free trial to keep year-end packs export-ready. Pair this with the free tax calculator for indicative UK and Ireland planning figures only.

Owner-managers watching distribution reform should read our company distributions consultation briefing (responses due 14 September 2026). Sole traders on Making Tax Digital should keep quarterly records current ahead of the August 2026 ITSA update deadlines.