Do you need to complete a Self Assessment tax return?

More than 12.1m people a year are required to fill out and file a Self Assessment tax return. Usually, about a million people miss the online filing deadline (31 January), which means they have to pay an automatic £100 late-filing penalty. Among them are many people who genuinely have no idea that they need to file a Self Assessment tax return because they earned taxable income.

Not everyone in the UK has to complete a Self Assessment tax return, of course. In fact, less than a fifth of the UK population does. But, are you one of them and if so, how do you register for Self Assessment?

Who must complete a Self Assessment tax return?

You must complete and file a tax return if, in the last tax year (which runs from 6 April to 5 April) you:

• were self-employed as a sole trader and earned more than £1,000 (before deducting any tax relief/expenses)
• earned taxable income from trading on popular platforms such as eBay, Amazon, Etsy, etc
• were a partner in an ordinary business partnership
• had total taxable income of more than £150,000
• received taxable income from renting out land or property (including taxable Airbnb income)
• need to pay Capital Gains Tax on the gain you made after selling something that increased in value (eg a business, property that isn’t your main home, personal possession for £6,000 or more, such as jewellery, paintings, antiques, but not your car, etc)
• had to pay the High Income Child Benefit Charge
• received taxable income from savings, investments and/or dividend payments
• earned income from overseas but are tax resident in the UK
• receive taxable tips and commission.

Why else might you complete a Self Assessment tax return?

You might choose to fill in a Self Assessment tax return to claim some Income Tax reliefs, or to prove you’re self-employed, perhaps to claim Tax-Free Childcare or Maternity Allowance, or to pay voluntary National Insurance contributions to gain from the benefits this provides.

Need to know! You must let HMRC know by 5 October after the end of the tax year (5 April) if you need to complete a Self Assessment tax return and have not sent one before. 

What about limited company directors?

• If all of your income as a company director is taxed at source when you’re paid via the company payroll, you don’t need to register for Self-Assessment (unless you have other taxable income to report such as rental income).
• If HMRC has asked you to file a Self Assessment tax return, but you have no additional taxable income to report, you can ask for withdrawal of your “notice to file”.
• If, as well as wages via the company payroll, you receive share dividend payments, these can also be subject to tax if they exceed the annual allowance (£1,000 for the 2023/24 tax year; £500 for 2024/25) and you earn more than the Personal Allowance (£12,570 for 2023/24/25).
• If you don’t receive taxable share dividend payments, you may have to fill out and file a Self Assessment tax return (and any necessary supplementary tax return pages) if you receive taxable income from: renting out property or land; running a separate sole trader business; taxable savings, investments or pension payments; Child Benefit received if you or your partner’s annual income was more than £50,000; overseas income that’s taxable in the UK (eg renting out a villa overseas).

Who doesn’t need to file a Self Assessment tax return?

People who do not need to file a Self Assessment tax return include:

• those who only earn money from employment (ie they work for others and have no other taxable income to report).
• some landlords – if your annual gross income is £1,000 or less from renting out land or property, thanks to the property allowance, there’s no need to report this income to HMRC (although you may need to file a tax return to report other taxable income)
• some sole traders – if your annual gross income is £1,000 or less from your sole trader business, thanks to the trading allowance, you don’t have to report this income to HMRC (although you may need to file a tax return to report other taxable income)
• you can claim both the trading allowance and property allowance and there’s still no need to file a tax return
• You live overseas but earn UK taxable income from UK sources (eg pension, rental income, savings interest, wages). If you’re eligible for the UK Personal Allowance, you pay Income Tax on your income above that. If not, you pay tax on all of your taxable UK income.

What happens if you fail to submit a Self Assessment tax return?

If HMRC sends you a Self Assessment tax return or notice to file one online, by law, you must do so, even if you haven’t earned any taxable income in that tax year. Alternatively, you can contact HMRC to ask to have the tax return withdrawn.

If you do not file a tax return after you’ve been asked to do so, HMRC will charge you penalties. It will also send you an estimated bill, which you must pay. HMRC can take court action against you for payment (up to making you bankrupt). You’re advised to fill out a tax return so that the correct amount can be calculated.

If you need to report taxable income to HMRC and knowingly do not, you’re guilty of tax evasion (ie deliberately avoiding paying tax due), which can bring serious consequences (financial penalties in most instances, but imprisonment for the worst transgressions).

Need to know! If you should have been reporting taxable income but haven’t, the consequences will be much less serious if you disclose the untaxed income to HMRC, cooperate fully with any investigation and pay any tax due ASAP.

How to register for Self Assessment

You register for Self Assessment online via the Government Gateway platform. Then each year you must complete and file a Self Assessment tax return (SA100), plus any required supplementary pages.

You must register for Self Assessment by 5 October following the end of the tax year (5 April) in which you earned taxable income. If you’ve registered before, you just need to sign in to your existing account to file your latest SA100 (contact HMRC for assistance if you’ve lost your account log-in details) or you can use third-party software like GoSimpleTax.

When registering for Self Assessment for the first time you’ll need to give your: full name (and any previous names), current address (and date you moved in), date of birth, gender, phone number, email address and National Insurance number. You’ll also be asked whether you’ve registered before for Self Assessment.

HMRC will then create an account for you and you’ll receive a letter with your Unique Taxpayer Reference (UTR) number within 10 days (21 if you’re based overseas). You’ll need your UTR to file your Self Assessment tax return. You’ll also then receive another letter with an account activation code.

Blog content is for information purposes and over time may become outdated, although we do strive to keep it current. It's written to help you understand your Tax's and is not to be relied upon as professional accounting, tax and legal advice due to differences in everyone's circumstances. For additional help please contact our support team or HMRC.