What is the HMRC Gateway?

By Ben Davies · Updated 26 September 2026

The HMRC Government Gateway is an online authentication system that lets you access HMRC's digital services. It is how you (or software acting on your behalf) log in to submit tax returns, including CT600 Corporation Tax returns.

Why you need it

To file a nil CT600 for your dormant company, you need Government Gateway credentials — a user ID and password. These authenticate you with HMRC and prove you are authorised to file on behalf of the company.

HMRC's free filing service — "File your accounts and Company Tax Return", known as CATO — closed on 31 March 2026. A CT600 now has to go through commercial software; paper is allowed only with a reasonable excuse or for a return in Welsh. We handle nil CT600 filing alongside your dormant accounts — see how it works.

How to get an account

If the company has filed with HMRC online before, it probably already has a Government Gateway account. If not:

1. Go to the HMRC online services page on GOV.UK
2. Create an organisation account
3. Enrol for Corporation Tax using your company's UTR (it's on the CT41G letter HMRC sends after incorporation)

The process involves identity verification and may take several days.

How we handle your credentials

When you file through DormantFile, your Gateway credentials are used once to authenticate the submission and never stored. We transmit them directly to HMRC at the point of filing. See our security page for details.

Forgotten your credentials?

You can reset your password through the Government Gateway service. If you have lost your user ID, use the "Problems signing in" recovery options on the sign-in page, or call HMRC's Online Services Helpdesk on 0300 200 3600.

Read the full guide: How to file a nil CT600 tax return with HMRC