My dormant company has started trading: what now?

In short: A dormant company that starts trading again must tell HMRC within 3 months of restarting, by registering for Corporation Tax again in its business tax account (GOV.UK: restarting a non-trading or dormant company; GOV.UK: Corporation Tax trading and non-trading). A new Corporation Tax accounting period starts on the day trading restarts. Its CT600 is due 12 months after the company's year end, and any tax 9 months and 1 day after it.

Work out each date for your year end with the Corporation Tax deadline calculator, or take the 30-second check to see whether Taxley fits your company.

Key facts (checked on 29 September 2026)

What should you do when a dormant company starts trading again?

Tell HMRC within 3 months (GOV.UK: Corporation Tax trading and non-trading), then run the company as an active one: its Corporation Tax accounting period now starts on the restart date, it files normal accounts at Companies House instead of dormant accounts, and it pays any Corporation Tax and files a full CT600 for that period (GOV.UK: restarting a non-trading or dormant company).

This checklist puts the jobs in order:

1. Note the restart date. It is the first day of the new Corporation Tax accounting period.
2. Tell HMRC within 3 months by registering for Corporation Tax again in the company's business tax account.
3. Register for VAT or PAYE if the business needs it, for example before the company pays its first salary.
4. Keep records from the first day of trading: sales, costs, bank statements and anything bought for the business.
5. File the year's accounts at Companies House within 9 months of the year end, as normal accounts rather than dormant accounts.
6. Pay any Corporation Tax 9 months and 1 day after the accounting period ends.
7. File the CT600 with full statutory accounts within 12 months of the year end.

What counts as starting to trade for Corporation Tax?

More than a first sale. GOV.UK says trading includes buying, selling, renting property, advertising, employing someone or getting interest, so a company that places its first advert or starts earning bank interest is no longer dormant for Corporation Tax (GOV.UK: dormant for Corporation Tax).

HMRC's guidance describes a company as active when it is, for example, carrying on a business activity such as a trade or professional activity, or buying and selling goods with a view to making a profit or surplus (GOV.UK: Corporation Tax trading and non-trading). Dormant for Companies House is a separate test, based on whether the company had any significant transactions in its financial year (GOV.UK: dormant for Companies House). The dormant company tax return guide sets out both tests side by side.

How do you tell HMRC the company is trading again?

Sign in to the company's business tax account with its Government Gateway user ID and password and register for Corporation Tax again, which is how GOV.UK says to tell HMRC a dormant company has restarted trading (GOV.UK: restarting a non-trading or dormant company). The deadline is 3 months after the new accounting period begins.

HMRC calls its online registration service the best way to do this, and it also accepts a letter that gives details such as the date the accounting period started, the date the company intends to prepare accounts to and the nature of its business (GOV.UK: Corporation Tax trading and non-trading). The 3-month limit is in section 55 of the Finance Act 2004, which covers any accounting period that doesn't immediately follow a previous one, as happens after a dormant spell. The section excuses a company with a reasonable excuse, but a company without one can be charged a penalty for giving notice late.

When does the new accounting period start?

On the day the company restarts business activities, not on the first day of its accounts year (GOV.UK: restarting a non-trading or dormant company). If the company keeps its accounting reference date, the period runs from the restart date to the next year end, so the first CT600 usually covers fewer than 12 months while the statutory accounts still cover the whole year.

GOV.UK's own example uses a 30 September year end and a restart on 1 May: the company prepares accounts for the usual year, sends them to Companies House and uses them to complete a Company Tax Return for 1 May to 30 September. Here is the same example with dates, for a restart on 1 May 2026:

From 1 October 2026 the accounts and the accounting period line up again, running from 1 October to 30 September each year. The accounting period, financial year and tax year guide explains how the terms differ.

Does a short first period change the Corporation Tax bill?

The rates stay the same, but the limits shrink: the £50,000 lower limit and £250,000 upper limit for marginal relief are proportionately reduced when an accounting period is shorter than 12 months (GOV.UK: Marginal Relief for Corporation Tax). A short first period therefore reaches the 25% main rate at a lower profit.

For the 153-day period from 1 May to 30 September 2026, the lower limit becomes about £20,959 (£50,000 × 153 ÷ 365) and the upper limit about £104,795. Profits up to the lower limit pay the 19% small profits rate, profits above the upper limit pay the 25% main rate, and marginal relief applies in between (GOV.UK: Corporation Tax rates). The limits are also divided by the number of associated companies plus one. The Corporation Tax calculator takes the period's start and end dates, so it applies the shorter limits for you.

Do you still file a return for the months the company was dormant?

Usually not. The dormant months fall outside the new accounting period, and a company that has told HMRC it is dormant doesn't file another return unless HMRC sends a further notice to deliver one (GOV.UK: dormant for Corporation Tax). If a notice arrives for a dormant period, answer it with a nil CT600 showing the company was dormant.

A nil return is still filed online, and HMRC's own filing service closed on 31 March 2026, so it goes through commercial software (GOV.UK: filing if you previously used the HMRC online service). Dormant company tax return software: file a nil CT600 online explains how Taxley files a nil CT600 for £9.50 (promotion price until 31 Dec 2026; £19.00 from 1 Jan 2027) and files any dormant accounts at Companies House at no extra cost. If a notice covers dates on both sides of the restart, ask HMRC's Corporation Tax general enquiries which returns it expects.

Which accounts does the company file at Companies House now?

Normal annual accounts instead of dormant accounts, due 9 months after the year end (GOV.UK: restarting a non-trading or dormant company). You don't need to tell Companies House that trading has restarted: GOV.UK says the next set of non-dormant accounts shows the company is no longer dormant (GOV.UK: dormant for Companies House).

Most small trading companies can file micro-entity or small company accounts. GOV.UK treats a company as a micro-entity if it has any 2 of a turnover of £1 million or less, £500,000 or less on its balance sheet and 10 employees or less; the small company limits are £15 million, £7.5 million and 50 employees (GOV.UK: micro-entities, small and dormant companies). A small company can choose to send Companies House less than the full accounts, as our guide to filleted, abridged and full accounts explains, but HMRC receives the full statutory accounts with the CT600. The confirmation statement carries on each year as before.

When is the Corporation Tax payment due?

9 months and 1 day after the accounting period ends, for a company with taxable profits of up to £1.5 million, quoting the 17-character payment reference for that period (GOV.UK: pay your Corporation Tax bill). For a period ending 30 September 2026 that is 1 July 2027, three months before the CT600 is due.

The payment reference is on HMRC's notice to deliver your tax return and in the company's HMRC online account. Our guide on how to pay Corporation Tax covers the payment methods, HMRC's bank details and what to do if the company can't pay on time. If the company has no Corporation Tax to pay for the period, tell HMRC, or it will keep sending payment reminders (GOV.UK: tell HMRC no payment is due); the CT600 is still due.

Does the company need to register for VAT or PAYE?

Only if the business needs them. The company must register for VAT if its taxable turnover for the last 12 months goes over £90,000, or is expected to in the next 30 days (GOV.UK: register for VAT). It must register as an employer before its first payday, even to pay only its director (GOV.UK: register as an employer).

A company that stayed registered for VAT while dormant should have been sending nil VAT returns, and GOV.UK says a dormant company not planning to restart in the same tax year should close its PAYE scheme (GOV.UK: dormant for Corporation Tax). If the scheme was closed, register again before paying anyone, but no more than 2 months before the first payday.

Can Taxley file the first return after a dormant company restarts?

Yes, if trading restarted on the first day of the company's accounts year. Taxley (taxley.co.uk), UK online software that prepares and files the Company Tax Return (CT600) with HMRC and the annual accounts with Companies House, then files the CT600 with iXBRL accounts and computations for one fee.

For periods of up to 12 months, Taxley's return and accounts cover the same dates. It can't file a CT600 that starts later than the accounts, so if trading restarted part-way through the year, as in the 1 May example, file that first year's return with other CT600 software; Taxley fits from the next full year. Taxley has filed accounts at Companies House since 28 September 2026, once the return is paid.

The fee includes filing the accounts at Companies House: £44.50 (promotion price until 31 Dec 2026; £89.00 from 1 Jan 2027) with micro-entity accounts or £84.50 (promotion price until 31 Dec 2026; £169.00 from 1 Jan 2027) with small-company accounts. Taxley doesn't tell HMRC the company is active or register it for VAT or PAYE; you do those yourself. Take the 30-second check to see whether Taxley fits your company, and see how Taxley files a dormant company's return for any nil return HMRC asks for.

Frequently asked questions

Do I need to tell Companies House my company is no longer dormant?

No. GOV.UK says you don't need to tell Companies House when trading restarts. The next accounts you file, which are normal accounts rather than dormant accounts, show that the company is no longer dormant. The confirmation statement continues each year as before.

How long do I have to tell HMRC my dormant company is trading?

3 months from the start of the new Corporation Tax accounting period, which begins on the day the company restarts business activities. Register for Corporation Tax again through the company's business tax account, using its Government Gateway user ID and password.

Does my first CT600 after dormancy cover the whole year?

Not usually. It covers the accounting period from the restart date to the company's year end, while the statutory accounts sent with it cover the full accounts year. From the next year, the accounts and the CT600 cover the same 12 months.

Do I pay Corporation Tax for the months the company was dormant?

No. A dormant company with no trade and no other income has no taxable profit, and the dormant months fall outside the new accounting period. Corporation Tax is worked out on the profits of the period that starts when trading restarts.

Does earning bank interest end a company's dormant status?

Yes, for Corporation Tax. GOV.UK lists getting interest alongside buying, selling, renting property, advertising and employing someone as trading, so a company earning interest isn't dormant for Corporation Tax even if it does nothing else, and it should tell HMRC it is active.

General information, not personalised tax or accounting advice.