Everything you need to know before you complete a Self Assessment tax return

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A Self Assessment tax return can look very daunting, but if you’re prepared, organised and understand what you’ll be asked for they’re a lot simpler than they look.

Do I need to fill in a Self Assessment tax return?

Yes, if:

  • your self-employment income was more than £1,000
  • your income from renting out property was more than £2,500 (you will need to contact HMRC if it was between £1,000 and £2,500)
  • you earned more than £2,500 in untaxed income, for example from tips or commission.
  • your income from savings or investments was £10,000 or more before tax.
  • you need to pay Capital Gains Tax on profits from selling things like shares or a second home.
  • you’re a director of a company (unless it was a non-profit organisation, such as a charity)
  • you, or your partner’s, income was over £50,000 and you’re claiming Child Benefit you have income from abroad you need to pay tax on, or you live abroad but have an income in the UK.
  • your taxable income was over £100,000
  • if you earn over £46,351 in the 2018/19 tax year (£50,001 for 2019/20) and make pension contributions you may have to complete an assessment to claim back the extra tax relief you’re owed
  • you are a trustee of a trust or registered pension scheme
  • your State Pension was more than your personal allowance and was your only source of income
  • you received a P800 from HMRC saying you did not pay enough tax last year.

You can also fill in a Self Assessment tax return if you want to make voluntary Class 2 National Insurance Contributions (NICs) to help you qualify for benefits such as the State Pension.

You do not need to fill in a Self Assessment tax return if you’re an employee who has paid tax through the Pay As You Earn (PAYE) system, unless you earnt over £100,000.

Find out if you need to fill in a Self Assessment tax return on Gov.uk

How to register for a Self Assessment tax return?

If you’ve never submitted a return before, you will first need to register for Self Assessment. There are different ways to register if you’re self-employed, not self-employed but need to declare income, or if you’re in a partnership.

Find out more and register on the Gov.uk website.

Once you have registered, you will be sent your Unique Taxpayer Reference (UTR).

If you want to submit your Self Assessment form online, you will then need to set up a Government Gateway account. To do this, follow the instructions in the letter containing your UTR.

Once you’ve set-up the account you will get an activation code in the post, which you need to complete the set-up of your Gateway account.

If you have submitted Self Assessment tax returns before, you will need your old UTR to register and set up the account.

It’s best to make sure you can access you Gateway account before you try and submit your Self Assessment to save time if for any reason you can’t log in.

What are the Self Assessment deadlines?

You submit tax returns for tax years, not calendar years, and you do this in arrears.

For example, for the 2018/19 tax year, running 6 April 2018 to 5 April 2019, you would:

  • need to register for Self Assessment by 5 October 2019 if you’ve never submitted a return before
  • submit your return by midnight 31 October 2019 if filing a paper tax return
  • submit your return by midnight 31 January 2020 if filing online
  • pay the tax you owe by midnight 31 January 2020.

If you fail to meet one or more of these deadlines, you might be charged a penalty fee.

Find out more about Self Assessment deadlines on Gov.uk.

What information will I need to fill in a Self Assessment tax return?

If you’ve never filled in a self-assessment tax return before, it can look very daunting. However, once you understand the process, it’s relatively simple, as long as you have all the information you need.

Before you start, make sure you have:

  • your 10-digit Unique Taxpayer Reference (UTR)
  • your National Insurance number
  • details of your untaxed income from the tax year, including income from self-employment, dividends and interest on shares
  • records of any expenses relating to self-employment
  • any contributions to charity or pensions which might be eligible for tax relief
  • P60 or other records showing how much income you received which you’ve already paid tax on.

It’s also a good idea to read the relevant HMRC helpsheets, particularly on the extra sections, or supplementary pages, relating to why you’re filling in the Self Assessment tax return.

You can find and download the helpsheets on the Gov.uk website.

If you’re filling in your Self Assessment form online, you can also find helpful online by clicking the ‘?’ next to the different fields.