Restarting a dormant company is one notification, four deadlines and one trap.
The notification goes to HMRC, not Companies House, and it is due within 3 months of the start of your new accounting period — a statutory obligation, not a courtesy. The trap is that your Corporation Tax accounting period begins when activity restarts, while your Companies House year end does not move. Your first Company Tax Return after the restart therefore covers a shorter period than your accounts.
Step 1: tell HMRC — within 3 months
This is the step with a legal deadline attached. Section 55 of the Finance Act 2004 requires a company to give notice to HMRC of the beginning of any accounting period that does not immediately follow the end of a previous accounting period. That is exactly what a restart is: the company had no Corporation Tax accounting period while it was dormant, and a new one opens the day activity resumes.
The notice must be in writing, must state when the accounting period began, and must be given not later than three months after the beginning of the accounting period.
Running alongside it is the separate — and more expensive — duty to notify HMRC that the company is chargeable to Corporation Tax, under paragraph 2 of Schedule 18 to the Finance Act 1998. Missing that one is a failure to notify penalty under Schedule 41 to the Finance Act 2008, charged as a percentage of the tax left unpaid. A reasonable excuse defence exists, but it only holds while the excuse lasts.
The three months run from the day the company restarted, not the day you remembered. HMRC’s guidance on trading and non-trading states the same deadline; its dedicated restart page does not repeat it, which is why so much published content omits it.
How to do it. Sign in to the company’s business tax account with its Government Gateway user ID and register for Corporation Tax again, adding Corporation Tax services to the account if it has never had them.
Writing to Corporation Tax Services, HM Revenue and Customs, BX9 1AX also works. HMRC lists what the letter must contain: company name and number, when the accounting period started, the date to which accounts will be prepared, principal place of business, nature of the business, every director’s name and home address, any business taken over, the parent company if there is one, and the date any PAYE obligation first arose. Two requirements are easy to miss: the letter must be signed by a company director or the company secretary, and it must include a declaration that the information given is correct and complete.
Step 2: do not tell Companies House
There is no restart notification at Companies House. Dormancy there is evidenced by the accounts you file, so the next set of non-dormant accounts does the job on its own.
What does not change: the confirmation statement is still due every 12 months, within 14 days of the end of the review period, £50 online or £110 on paper.
Step 3: sort out VAT
Which move you make depends on what you did when the company went dormant.
- You cancelled the registration. Register again. The compulsory tests are the same as for any business: taxable turnover over £90,000 in the last rolling 12 months, or an expectation of exceeding £90,000 in the next 30 days alone. Below that you can register voluntarily, which is often the right call where the company reclaims input VAT or sells to VAT-registered customers.
- You kept the registration and filed nil returns. Nothing to do beyond filing real figures from the first live period. Returns are due 1 calendar month and 7 days after the period end, under Making Tax Digital.
Step 4: reopen PAYE
If you closed the PAYE scheme, you register as an employer again to get an employer PAYE reference.
Two timing rules matter. You must register before the first payday, and you cannot register more than 2 months before you start paying people. Start too early and the registration is refused; start too late and you are running payroll without a reference. You must register even if the only person on the payroll is you as the sole director. If the reference has not arrived in time, run the payroll, store the full payment submission, and send it as a late FPS.
The accounting period trap
This is the part that generates wrong returns.
Your Companies House accounting reference date stays exactly where it is. Your Corporation Tax accounting period begins when the company restarts business activities. HMRC’s recommended approach is to leave the ARD alone and prepare statutory accounts as usual for the full 12 months to that date — which makes the end of the CT accounting period and the accounting reference date the same, even though the start dates differ.
The result: your first Company Tax Return after a restart covers a shorter period than your accounts.
Worked example
A dormant company has an accounting reference date of 30 September. It restarts trading on 1 May 2027.
| Item | Period covered | Deadline |
|---|---|---|
| Statutory accounts | 1 Oct 2026 – 30 Sep 2027 (12 months) | — |
| Accounts to Companies House | as above | 30 June 2028 (9 months after the year end) |
| Corporation Tax payment | 1 May – 30 Sep 2027 | 1 July 2028 (9 months and 1 day) |
| Company Tax Return (CT600) | 1 May – 30 Sep 2027 (5 months) | 30 September 2028 (12 months) |
Three things fall out of that table.
The payment deadline lands roughly three months before the filing deadline. You have to work out the liability well before the return is due — which catches out almost everyone in their first year back.
The accounts are not dormant accounts. They cover a period containing significant accounting transactions, so they are ordinary micro-entity or small company accounts. Dormant accounts would be rejected.
A short accounting period pro-rates the Corporation Tax limits. The small profits rate of 19% applies to profits up to £50,000 and the main rate of 25% above £250,000, but both limits are reduced proportionately for a period shorter than 12 months, and divided again by the number of associated companies including the company itself. For a 5-month period they become roughly £20,833 and £104,167. (HMRC’s guidance at CTM03930 does the reduction by days, not months, so on the 153 days from 1 May to 30 September 2027 the strict figures are £20,958.90 and £104,794.52.)
Check the accounting period dates HMRC shows in the business tax account after you register. HMRC writes to confirm them, and you should tell HMRC if they are wrong — filing software that defaults to the accounts period will produce a return for the wrong dates.
Filing the first return
Since 1 April 2026 you must use commercial software to file a Company Tax Return. HMRC’s free CATO service closed on 31 March 2026, so the DIY route is gone; paper is only available with a reasonable excuse or if you file in Welsh. The return goes in with full statutory accounts and computations in iXBRL. Companies House accounts filing remains free, and web filing still works for accounts until April 2028.
Frequently asked questions
How long do I have to tell HMRC my dormant company has restarted?
Three months from the start of the new Corporation Tax accounting period, which begins on the day the company restarts business activities. This comes from section 55 of the Finance Act 2004. Separately, you must notify HMRC that the company is chargeable to Corporation Tax under paragraph 2 of Schedule 18 to the Finance Act 1998, and missing that carries a failure to notify penalty under Schedule 41 to the Finance Act 2008.
Do I need to tell Companies House that my company has restarted trading?
No. There is no restart notification at Companies House. The next set of non-dormant accounts you file shows the company is trading again. The confirmation statement is due every 12 months either way.
Why does my first Company Tax Return cover a shorter period than my accounts?
Because your Corporation Tax accounting period begins when the company restarts business activities, while your Companies House accounting reference date does not move. If you keep the same year end, the accounts cover the full 12 months and the return covers only the part of the year from the restart date to that year end.
Do I need to register for VAT again after restarting?
Only if you cancelled the registration. You must register if taxable turnover in the last 12 months has gone over £90,000, or you expect it to exceed £90,000 in the next 30 days, and you can register voluntarily below that. If you kept the registration and filed nil returns while dormant, you simply start filing real figures again.
When do I reopen the PAYE scheme?
Register as an employer before the first payday, and no more than 2 months before you start paying people. You must register even if you are the only director on the payroll. If the employer PAYE reference has not arrived in time, run the payroll, store the full payment submission and send it as a late FPS.
Getting the restart right
The company coming back to life is the easy part. Getting the notification in inside three months, splitting the Corporation Tax period from the accounts period, and paying before the return is due are where the first year goes wrong.
SmartFiling handles dormant company restarts on a fixed fee, including the HMRC notification, the accounts, the Company Tax Return and the confirmation statement. Every filing is reviewed and signed off by an ICAEW Chartered Accountant, and everything is done online.
