Who needs it
- Sole traders whose self-employed income was over £1,000 in the tax year, before deducting anything they can claim tax relief on.
- Partners in a business partnership.
- Anyone who owes Capital Gains Tax on something they sold or gave away.
- Anyone who owes the High Income Child Benefit Charge and isn't paying it through PAYE.
- People with untaxed income, such as rent, tips, commission, savings interest, dividends or foreign income, may also need to file. HMRC's online checker tells you for certain.
What you need before you start
- Your 10-digit Unique Taxpayer Reference (UTR) and your National Insurance number.
- Your Government Gateway user ID and password, if you file online.
- P60s, P45s and P11Ds for any employment in the year.
- Business, rental and investment records: income, expenses, interest certificates and dividend vouchers.
- Details of pension contributions and Gift Aid donations you want relief on.
How to file SA100
- 1Register for Self Assessment by 5 October after the end of the tax year if you haven't filed before. HMRC then posts your UTR.
- 2Work out which supplementary pages apply: employment (SA102), self-employment (SA103S or SA103F), partnership (SA104), UK property (SA105), foreign income (SA106), capital gains (SA108) and residence (SA109) are the common ones.
- 3File online through your HMRC account or commercial software, or complete the paper SA100 and supplementary pages from GOV.UK.
- 4Post a paper return to Self Assessment, HM Revenue & Customs, BX9 1AS. HMRC must receive it by the paper deadline, not just have it posted.
- 5Pay any balance, and any first payment on account, by 31 January. A second payment on account, if you make them, is due by 31 July.
What the SA100 covers
The SA100 is the core of every Self Assessment return. It collects your personal details, UK interest and dividends, pension and Gift Aid payments and a handful of reliefs. HMRC describes it as the form for reporting income, claiming tax reliefs and asking for any repayment due.
Most other income goes on supplementary pages that sit alongside it. HMRC lists SA102 for employees and company directors, SA103S or SA103F for self-employment, SA104 for partnerships, SA105 for UK property, SA106 for foreign income, SA107 for trusts and estates, SA108 for capital gains and SA109 for residence and the remittance basis. SA101 covers less common income and reliefs.
Online, the supplementary pages are built into the return and appear when you say you had that kind of income. On paper, you download and send each one yourself.
Online or paper
Filing online gives you three more months than paper: the online deadline is 31 January, the paper one is 31 October, both after the end of the tax year. Online, you can print your SA302 tax calculation 72 hours after you submit.
If you want an amount owed collected through your tax code instead of paid in one go, HMRC needs the online return by 30 December. Miss that and you pay another way.
If you register after 5 October, HMRC sends a notice with a filing deadline three months from its date. The 31 January payment date doesn't move.
Scotland
The SA100 is the same form across the UK. If you live in Scotland you pay Scottish Income Tax on wages, pensions and most other taxable income, so the bands applied to your return differ from the rest of the UK. Savings interest and dividends are taxed at the same rates as the rest of the UK.
Common mistakes
- Missing the paper deadline and posting the return anyway. HMRC's advice is to file online instead, which still has three months to run.
- Leaving out a supplementary page. The SA100 on its own doesn't cover self-employment, property or capital gains.
- Using the short self-employment page (SA103S) when turnover was above the VAT registration threshold. That needs the full SA103F.
- Registering after 5 October. HMRC still expects payment by 31 January, even though it sets a later filing deadline.
- Throwing records away too soon. HMRC expects them kept for at least five years after the 31 January deadline.
Related
What else will you need?
- SA103SA103 self-employment pagesSA103 is the self-employment section of the Self Assessment return.
- Where to find itFind your UTRYour Unique Taxpayer Reference (UTR) is a 10-digit number HMRC gives you when you register for Self Assessment or set up a limited company.
- Where to find itGet your SA302An SA302 is HMRC's calculation of your tax for a year, used as proof of income, for example by self-employed mortgage applicants.
- ChecklistSelf Assessment documents checklistBefore you file a Self Assessment return, gather your UTR and National Insurance number, your Government Gateway sign-in, any P60, P45 or P11D, your business and rental income and expense records, interest and dividend statements, details of anything you sold that may have made a gain, and records of pension contributions and Gift Aid.PDF
- 64-864-8 agent authorisationForm 64-8 is the paper form you sign to let a paid agent, such as an accountant, deal with HMRC for you.
- SA1SA1 Self Assessment registrationSA1 is HMRC's postal form for registering for Self Assessment when you aren't self-employed, for example because you owe Capital Gains Tax or have income from property, a pension or a trust.
- SA102SA102 employment pagesSA102 is the employment section of the Self Assessment return.
- SA105SA105 UK property pagesSA105 is the UK property section of the Self Assessment return.
- SA108SA108 capital gains pagesSA108 is the capital gains summary in the Self Assessment return.
Rather we did it?
Countify can handle this for you, for a fixed fee agreed upfront.
Questions
Frequently asked questions.
Do I need to send an SA100 if I'm employed?
Not usually, if all your income is taxed through PAYE. You'll need a return if you also have self-employed income over the trading allowance, owe Capital Gains Tax or owe the High Income Child Benefit Charge outside PAYE. HMRC's online checker gives a definite answer.
Can I still get a paper SA100?
Yes. HMRC publishes the current SA100 and its supplementary pages as PDFs on GOV.UK. A paper return has an earlier deadline of 31 October and must reach HMRC by then.
Where do I send a paper return?
UK residents post it to Self Assessment, HM Revenue & Customs, BX9 1AS. If you live outside the UK, HMRC gives a separate Newcastle address on the SA100 page.
How long should I keep my records after filing?
At least five years after the 31 January submission deadline for that tax year. If you file more than four years late, HMRC asks you to keep them for 15 months after you send the return.
Checked against GOV.UK on · Reviewed by Kamran Ishaq FCCA, Founder & CEO, on .
Sources: Self Assessment tax return (SA100) (opens in a new tab) (HM Revenue & Customs); Self Assessment deadlines (opens in a new tab) (HM Revenue & Customs); Self Assessment: who must send a tax return (opens in a new tab) (HM Revenue & Customs); Business records if you're self-employed: how long to keep them (opens in a new tab) (HM Revenue & Customs); Income Tax in Scotland (opens in a new tab) (HM Revenue & Customs).
Countify is an independent accountancy practice. We aren't part of, or endorsed by, HM Revenue & Customs. Always file using the official form or service.
Contains public sector information licensed under the Open Government Licence v3.0 (opens in a new tab).