Every UK limited company must file annual accounts with Companies House and, separately, a Company Tax Return with HMRC once HMRC has sent it a notice to deliver one. A private company has 9 months from the end of its accounting reference period to file with Companies House; a public company has 6 months. The tax return is due 12 months after the end of the accounting period, but the tax itself is due after 9 months and 1 day. The joint online service that let small companies file both at once closed on 31 March 2026, and from 1 April 2028 Companies House will accept accounts only through commercial software.
Two filings, two regulators
Companies House and HMRC want different things for different purposes, which is why the filing splits in two:
- Companies House. Statutory accounts, approved by the directors, placed on the public register. What has to be filed depends on the company's size: micro-entities and small companies can file a reduced set, and small companies can currently file filleted accounts without the profit and loss account or directors' report;
- HMRC. The Company Tax Return (CT600), filed with the company's annual accounts and tax computations. None of this goes on the public register.
Deadlines
| Filing or payment | Deadline |
|---|---|
| Accounts to Companies House (private company) | 9 months after the end of the accounting reference period |
| Accounts to Companies House (public company) | 6 months after the end of the accounting reference period |
| First accounts covering more than 12 months | Later of 21 months from incorporation (private) and 3 months after the end of the accounting reference period |
| Corporation tax payment (not paying by instalments) | 9 months and 1 day after the end of the accounting period |
| Company Tax Return | 12 months after the end of the accounting period |
The Companies House deadlines are in section 442 of the Companies Act 2006. Two traps catch new companies. First, the first accounts deadline is driven by the incorporation date, not just the year end. Second, the tax payment falls due three months before the return; a company that waits for the return deadline to work out its tax will already be paying interest. Companies with taxable profits above £1.5 million generally pay by quarterly instalments instead.
How to file with Companies House now
Until 31 March 2028 there are three routes:
- Companies House online service. Available for dormant accounts for companies that have never traded, micro-entity accounts, abridged accounts and small full accounts. You need a Companies House password and the company's authentication code, and the accounts must be approved by the directors before you file;
- Commercial software. Accounts produced and filed in iXBRL through accounting software or by an agent. This is the route for accounts the online service does not accept, and the one agents normally use;
- Paper. Still accepted for now, but slow and soon to end.
Companies House confirmed on 9 June 2026 that from April 2028 all accounts must be filed through commercial software in iXBRL format, with web and paper filing closed for accounts. The same package of changes, under the Economic Crime and Corporate Transparency Act reforms, will:
- Require a profit and loss account. Small companies and micro-entities will have to deliver one, with an option to opt out of publishing it. Companies House says the details of the opt-out will be confirmed in due course;
- Remove abridged accounts. Small companies will instead file full accounts, with a balance sheet and profit and loss account, prepared under the small companies regime;
- Strengthen audit exemption statements. Companies claiming audit exemption will give an enhanced statement on the balance sheet;
- Require everything together. The component parts of the accounts and reports will have to be filed together;
- Limit shortening. The number of times a company can shorten its accounting reference period will be reduced.
Filing the Company Tax Return after the joint service closed
The "File your accounts and Company Tax Return" service, which many small companies used to file both at once without software, closed on 31 March 2026. HMRC's guidance is that from 1 April 2026 companies should use commercial software to file annual accounts and Company Tax Returns with HMRC. Paper returns are only accepted with a reasonable excuse or when filing in Welsh. If you used the old service, you now need software, or an agent, for the HMRC side, even if you continue to file accounts with Companies House online until 2028.
HMRC's guidance is that a return must still be filed where the company makes a loss or owes no corporation tax.
Penalties
Companies House late filing penalties are automatic and depend on how late the accounts are:
| Time after the deadline | Private company | Public company |
|---|---|---|
| Up to 1 month | £150 | £750 |
| 1 to 3 months | £375 | £1,500 |
| 3 to 6 months | £750 | £3,000 |
| More than 6 months | £1,500 | £7,500 |
The penalty doubles if the accounts are late two years in a row. An appeal needs a specific reason, with dates, showing the circumstances were outside the company's control.
HMRC penalties increased for returns with a filing date on or after 1 April 2026, under section 265 of the Finance Act 2026. A late Company Tax Return now attracts £200 at one day late and another £200 at three months. At six months HMRC estimates the tax and adds a penalty of 10% of the unpaid tax, with another 10% at twelve months. If a return is late three times in a row, the £200 penalties become £1,000 each. Under the previous rules the flat penalties were £100, rising to £500 for repeat failures.
A practical filing routine
Diarise three dates from the year end: tax payment at nine months and a day, Companies House at nine months, and the tax return at twelve. Prepare the accounts and tax computation together so the payment is based on a real number. Check now whether your software can file iXBRL accounts with Companies House, because the 2028 changes will remove abridged accounts and bring the profit and loss account onto the filing for every small company. Our guide to UK GAAP explains which accounting framework your filed accounts should follow.
Acumon prepares and files statutory accounts and Company Tax Returns for companies of every size. Our statutory accounts team handles both filings, and our iXBRL tagging and filing service suits companies that prepare their own accounts but need compliant software filing.