How to reactivate a dormant company

By Ben Davies · Updated 26 September 2026

Stop keeping this deadline in your head

If your company has been sitting dormant and you are ready to start trading, there are several things you need to do. The company does not automatically "wake up" — you need to notify the right people and get your admin in order.

Before you start

A quick note: DormantFile looks after dormant and non-trading companies only. We cannot help with reactivation, trading accounts, or Corporation Tax returns for active companies. If you are bringing a company back to life, we strongly recommend working with an accountant, at least for the transition period. The first set of trading accounts after a dormant period can be tricky to get right.

That said, here is what is involved so you know what to expect.

Step 1: Notify HMRC

This is the most important step. HMRC set up a Corporation Tax record for the company after incorporation and sent its UTR number (the company's 10-digit tax reference) on a letter called a CT41G — so even if the company has never traded, you are not registering from scratch. You need to tell HMRC that the company is now active, within three months of starting to trade. You can do this by:

Signing in to HMRC online services for the company
Calling HMRC's Corporation Tax helpline on 0300 200 3410
Writing to HMRC

You will need the company's UTR and the date the company started trading. If you can't find the UTR, you can ask HMRC to send it again.

From then on, HMRC will send a notice to deliver a Company Tax Return for each accounting period, and the returns will need to show the company's trading.

Step 2: Open a business bank account

If your dormant company does not have a bank account, you will need one before you start trading. Most business bank accounts require:

Proof of the company's incorporation (certificate of incorporation)
Details of directors and persons with significant control
An idea of the company's expected trading activity

Opening a business bank account can take anywhere from a few days to several weeks, so start early.

Step 3: Update your SIC codes

Your company's SIC code describes its business activity. If your company was dormant, it may have a generic SIC code (such as 99999 — "dormant company, no significant trading activity"). Update this to reflect your actual trading activity.

You can change your SIC codes when you next file a confirmation statement (CS01) with Companies House. You do not need to wait for the confirmation statement to be due — you can file one early to update the codes.

Step 4: File trading accounts for the first trading period

Once your company starts trading, you can no longer file dormant accounts. Your next set of annual accounts must show the company's financial position — for most reactivated small companies that means micro-entity or small-company accounts, not "full" accounts — even if trading activity was minimal.

The first accounting period after reactivation can be complex. It may cover a period where the company was partly dormant and partly trading. An accountant will know how to handle this correctly.

Your accounts will still be due 9 months after your accounting reference date, and your Corporation Tax return 12 months after the period end.

Step 5: Register for VAT (if applicable)

You must register for VAT if your taxable turnover exceeds the VAT threshold, which is currently £90,000 in a rolling 12-month period. You must also register if you expect to exceed this threshold in the next 30 days alone.

You can voluntarily register for VAT below this threshold if it makes sense for your business (for example, if most of your customers are VAT-registered businesses and you want to reclaim VAT on purchases).

Step 6: Register for PAYE (if hiring)

If you are going to employ anyone — including yourself as a director taking a salary — you need to register as an employer with HMRC and set up PAYE. You should do this before you make your first payment to an employee.

You can register for PAYE online via HMRC. Registration can take up to 15 working days, so plan ahead.

What about the transition period?

The move from dormant to trading creates a transition that affects your filings:

The accounting period in which you start trading will need trading accounts (micro-entity or small-company for most), not dormant accounts, even if the company was dormant for most of the period.
Your CT600 for that period will need to reflect the trading activity, not be a nil return.
If you were previously filing dormant accounts via DormantFile, you will need to cancel and switch to accounting software or an accountant for the trading period onwards.

This transition is exactly the point where professional help pays for itself. An accountant can ensure the changeover is handled correctly and nothing falls through the gaps.

Key points

Tell HMRC within three months that your company is trading — it already has a Corporation Tax record and UTR from incorporation.
Open a business bank account before you start trading.
Update your SIC codes via your next confirmation statement.
File trading accounts (not dormant accounts) for the first trading period — micro-entity or small-company for most.
Register for VAT if turnover will exceed £90,000, and for PAYE if you are hiring.
DormantFile cannot help with reactivation — we recommend an accountant for the transition from dormant to trading.