Guidance

Check how to submit a Self Assessment tax return using commercial software

Find out if you need to create a unique user ID and password to submit your Self Assessment tax return using commercial software.

• From: HM Revenue & Customs
• Published: 9 February 2026

You may need to create a unique Government Gateway user ID and password to submit a Self Assessment tax return through commercial software. This will allow your software to submit your Self Assessment tax return to HMRC.

If you use Making Tax Digital for Income Tax, you need to use a different process to authorise your software.

Before you start

Check that you have:

• registered for Self Assessment
• added Self Assessment as a tax to your personal or business tax account

You’ll need to know whether you sign in to HMRC with:

• Government Gateway — your user ID could be up to 12 characters
• GOV.UK One Login — your username is your email address

If you’re not sure which details you use, check the correct sign in details for HMRC online services.

If you sign in using Government Gateway

If you sign in to Self Assessment using Government Gateway, use the same details in your commercial software to connect it to HMRC to submit your tax return.

If you sign in using GOV.UK One Login

If you sign in to Self Assessment using GOV.UK One Login, you will need to create a unique Government Gateway user ID and password to connect your commercial software to HMRC when submitting your tax return.

Your unique Government Gateway user ID and password cannot be used to access services on GOV.UK.

Create a unique Government Gateway user ID and password

Follow the steps to create your unique Government Gateway user ID and password.

1. Use your GOV.UK One Login to sign in to your HMRC online account.

2. If you have signed in to your personal tax account, select:
   
   1. ‘Profile and settings’.
   2. ‘Manage’ next to ‘Sign in details’.
   3. ‘View’ next to ‘Commercial software guidance’.

3. If you have signed in to your business tax account, select:
   
   1. ‘Manage account’.
   2. ‘View or change your business tax account details’.
   3. ‘Manage your HMRC sign in details’.
   4. ‘View’ next to ‘Commercial software guidance’.

4. Read the guidance and select ‘Create Government Gateway details’.

5. Follow the steps until you have created a unique Government Gateway user ID and password. Your user ID will be emailed to you.

6. Enter your unique Government Gateway user ID and password into the relevant fields in your commercial software when submitting your Self Assessment tax return.

Published 9 February 2026