Self Assessment

A Self Assessment is the method that we use to do personal tax returns in the UK. When you earn untaxed income, you have to declare it to HMRC yourself. You then submit a Self Assessment tax return via an SA100 form, detailing all your income and expenses. You pay income tax on your profits.

What income is untaxed?

There are various reasons that you might have earned untaxed income. Here are a few of them:

  • Rental income
  • Capital gains from investments
  • Profit from selling assets (e.g. a house)
  • Self-employed income
  • Side gig income (e.g. you work full time but drive for Uber on the side)
  • Claiming pension tax relief
  • You earn more than £100,000

How to file a Self Assessment

You’re taxed on income that you earn each tax year. This runs from 6th April – 5th April every year, but you can choose to calculate it based on any 12 month period. If you do decide to do this, we’d recommend getting in touch with an accountant as this method can be more complicated – and you want to avoid getting unnecessary penalties.

You have to pay your tax bill by 31st January, the year following the tax period you’re paying for. For income earned between 6th April 2022 – 5th April 2023, for instance, you have to pay your bill by 31st January 2024.

You can pay your tax bill in various ways:

  • Online using a tax return service
  • Using an accountant
  • You can do it yourself via HMRC online, or by post

A few things to remember about Self Assessment

  • The most common reasons to do a Self Assessment are either to pay tax on your earnings outside your salaried employment, or to claim a tax rebate
  • You might need to do a Self Assessment even if your only income is from employment (and your employer already takes care of your taxes)

E.g. you earn over £100,000

E.g. you want to claim a tax relief

  • Once you register for Self Assessment, you have to submit a tax return every year until you tell HMRC that you don’t need to do one anymore. If you don’t, you’ll be fined
  • Starting from 6th April, if you sell a property for a profit, you have to use the Real Time Capital Gains Tax Service instead of Self Assessment

Frequently Asked Questions

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