Registering for Self Assessment

If you need to complete a Self Assessment tax return for the first time, you need to register with HM Revenue and Customs (HMRC). You'll also need to use the registration forms to tell HMRC if you become self-employed, even if you already complete a tax return.

On this page:

Why you might need to complete a tax return

If your circumstances change you may need to fill in a Self Assessment tax return. On the return you tell HMRC about new income or capital gains, or claim expenses or reliefs.

For example, you may have:

  • started your own business
  • untaxed income from property or investments
  • expenses to claim (you need a tax return if they're above £2,500)
  • Capital Gains Tax to pay

Check if you need to need to complete a tax return

Find out more about Capital Gains Tax

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Why and when you need to register for Self Assessment

You’ll need to register for Self Assessment before you complete your first tax return.

When you register you’ll give HMRC the information they need to set up the right records for you. This helps to make sure you pay the right amount of tax and National Insurance at the right time.

If you already complete a tax return and you become self-employed, you can use the same registration forms to tell HMRC. They will then update your tax and National Insurance records.

For other changes in circumstances, simply complete the relevant boxes or supplementary pages on your Self Assessment tax return.

When to register

It's best if you register with HMRC as soon as your circumstances change. The latest you can register is by 5 October after the end of the tax year for which you need a tax return. The tax year runs from 6 April one year to 5 April the next.

If, for example, you have tax to pay on rent from a property in the 2010-11 tax year, you need to let HMRC know by 5 October 2011.

If you register late you may have to pay a penalty.

Take care to tell HMRC about your tax on time (PDF 92K)

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Information you'll need before you register

You will need:

  • Your National Insurance number. In most cases you'll already have this, but if you haven't worked in the United Kingdom before you'll need to get one.
  • Your contact details and the contact details of your business, if you've started self-employment.
  • Your ten-digit Unique Taxpayer Reference number if you have previously completed a Self Assessment return. You’ll find this on letters or forms sent by HMRC about your tax return.
  • The date your circumstances changed.

Find out how to apply for a National Insurance number (Opens new window)

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How to register

How you register depends on your circumstances.

If you're self-employed

If you're working for yourself, you can register online for Self Assessment. It’s quick and easy. HMRC will use the information to set up the right National Insurance records for you too.

Register online for Self Assessment and National Insurance contributions

If you're starting or joining a new business partnership

If you’re starting or joining a new business partnership, both the partnership and each partner need to be registered for Self Assessment.

The partner nominated to receive and send in the partnership tax returns must complete the partnership registration form. It’s quick and easy and can be done online.

Register the partnership online for Self Assessment

You must register as a partner in the business if you’re an individual. HMRC will use the information you send to set up the right National Insurance records for you too.

You can do this online. It will help if you have information about the partnership to hand before you start, for example:

  • address and postcode
  • Partnership Unique Taxpayer Reference
  • Company registration number (if registered with Companies House)

Register online as a partner for Self Assessment and National Insurance contributions.

If a company, trust or another partnership becomes a partner in the partnership, it needs to be registered for Self Assessment too. The person responsible for the new partnership, for example, the trustee or company secretary, should complete and sign form SA402.

Download SA402 Register a partner for Self Assessment if they're not an individual (PDF 95K)

If you need a tax return for any other reason

You may need to complete a tax return because your circumstances have changed. You may, for example, have income from property or capital gains that you need to tell HMRC about. In this case you'll need to complete form SA1 Registering for Self Assessment.

Download SA1 Registering for Self Assessment and getting a tax return (PDF 31K)

Check if you need to need to complete a tax return

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What happens once you’ve registered for Self Assessment?

Once you’ve registered for Self Assessment, HMRC will set up your records and send you a letter with a ten-digit reference, called a Unique Taxpayer Reference or UTR. You should keep your Unique Taxpayer Reference in a safe place. You'll need it to register for HMRC Online Services or whenever you get in touch with HMRC.

You’ll then get a letter telling you when you need to send your first tax return. The letter will usually be in April, but it may be earlier if you need to send a tax return back for an earlier tax year. If you don't receive a notice or a tax return, you should contact HMRC.

Telephone or write to HMRC

Find out more about filing online

If you’ve started in business

If you're self-employed as a sole trader or a business partner, you’ll usually need to arrange to pay your Class 2 National Insurance contributions straight away too.

You may also need to register for VAT and the Construction Industry Scheme.

Find out about Class 2 National Insurance contributions and exceptions

How and when to register for VAT

What is the Construction Industry Scheme?

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More useful links

Authorising an accountant to deal with HMRC for you

Starting up in business - practical advice from Business Link (Opens new window)

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