A self-assessment tax return is actually known as an SA100 in HMRC speak. It’s the form individuals use in the UK to report untaxed income, claim tax reliefs and allowances, as well as tax refunds. The SA100 tax return is accompanied by a series of supplementary pages which capture additional types of information on income, but depending on an individual’s circumstances they may not need to fill any of these in at all. In this guide, we’ll look at the SA100 form in detail to help you understand what it covers and the information that needs to be entered into it.
Table of contents
1. What is an SA100 Form?
An SA100 form is the main tax return that individuals registered for self-assessment all need to submit to HMRC so they declare certain types of untaxed income. Even if an individual has none of the types of income mentioned on this form, it is mandatory to fill it in because it verifies other important information such as name, address and bank details for a tax refund.

2. What are the Main Sections in the SA100
A tax return is organised into different sections, each one focussing on a different topic so that HMRC can get to know an individuals situation and income can be declared, as well as claiming income tax allowances and reliefs.
2.1 Personal Details
In the first part of the return, an individual needs to confirm all their personal details such as name, address and marital status. For those filling in their tax return online, this will be pre-populated with the information HMRC holds on file. But any changes, such as a change in address, can be made at this point.
2.2 Supplementary Sections
Next, HMRC will want to know which additional sections need to be included with the tax return. The supplementary sections available are specifically designed for different forms of income and they are:
- Employees or company directors SA102
- Self-employment SA103S or SA103F
- Business partnerships SA104S or SA104F
- UK property income SA105
- Foreign income or gains SA106
- Capital gains SA108
- Non-UK residents or dual residents SA109
2.2 Income
Here individuals need to declare untaxed income:
- Bank interest and dividends
- Pensions and annuities
- Other taxable income** that isn’t included in the above categories or the supplementary pages.
** The other taxable income box can be used for the following:
- Casual cash in hand work not covered by the trading income allowance
- Business income received by someone even though their business has stopped trading
2.3 Tax Reliefs
In the next section of the SA100, an individual can notify HMRC about different income tax allowances and reliefs they wish to claim – broadly speaking these fall into the following sections:
2.3.1 Pension Relief
Where an individual has made contributions into a private registered pension that they would like to claim tax relief on, they can enter details about this here. Pension payments made to schemes where the provider has claimed tax relief at source on behalf of the individual should be entered gross of this figure. Details of this will be on annual pension statements or can be calculated manually by dividing total contributions by 80 and multiplying them by 20. Even if you are a higher rate taxpayer (20%) you need to gross your contributions up by the 20% rate. HMRC will give you the additional relief you are entitled to when they automatically work out your tax calculation once you’ve completed your tax return.
Remember to exclude any pension contributions made into employers pension schemes from this section.
2.3.2 Gift Aid
Gift aid is a UK tax incentive scheme that allows registered charities to claim back an extra 25p for every £1 of eligible donations made by individuals to them. In some cases, the person making the donation can also claim a tax rebate on their tax return. Higher rate tax payers will be entitled to additional tax relief.
Under the rules, the individual making the donation must have paid sufficient income tax and/or capital gains tax to cover the grossed up amount of the donation made, otherwise, the individual will be liable for repaying HMRC for the amount given to the charity.
2.3.3 Blind Persons Allowance
The Blind Person’s Allowance is an additional amount of personal allowance given to those who qualify to claim it. The additional allowance means anyone who is eligible to earn more before paying tax. For the tax year 2021/2022 that additional amount is £2,520, meaning the total personal allowance for those eligible becomes £15,090.
2.3.4 Student Loan Repayments
The student loan section of the SA100 lets HMRC know to make student loan repayments are necessary unless they are being dealt with by an employer. This is particularly relevant for someone who has chosen to go self-employed and has been notified that repayments need to begin. HMRC will request payment from the individual based on their earnings and then pass these onto the SLC on their behalf.

2.3.5 High Income Benefit Charge
The high income benefit charge is the repayment of child benefit for individuals earning between £50,000 and £60,000 (this is based on their and their partners combined income), including through self-employment.

2.3.6 Incorrectly Claimed Coronavirus Support
This is an individuals opportunity to repay any incorrectly claimed coronavirus income support money including:
- Coronavirus Job Retention Scheme (CJRS)
- Eat Out to Help Out Scheme
- Self-Employment Income Support Scheme (SEISS)
If HMRC is already in conversation with an individual regarding the topic of incorrectly claimed coronavirus support or an assessment has already been raised, then it shouldn’t be included here.

2.3.7 Marriage Allowance
The marriage allowance lets one partner transfer up to 10% of their unused personal allowance to another. In this section, an individual can elect for this transfer to take place and the unused amount added to their partners’ personal allowance by entering the details of the person they would like it transferred to.

2.3.8 Finishing the Tax Return
Finally, once all the relevant boxes have been completed and supplementary pages if necessary, the SA100 can be completed. The final part contains questions regarding where to make repayments, the option to ask HMRC to pay outstanding tax through a PAYE tax code, whether a tax advisor was used and the opportunity to share any other relevant information with HMRC.
3. How to Get a SA100 Form
You get a SA100 once you are registered for self-assessment, which means you have let HMRC know that you are receiving untaxed income such as bank interest, pensions, dividends or are self-employed
4. How to Fill in an SA100 Form
A tax return form is issued to UK taxpayers shortly after the tax year ends on 5 April and for most, it should be filled in online by the following 31 January. A paper version is available from HMRC but this needs to be submitted by 31 October.
5. How to Print an SA100 Form
You can print a tax return by going to the HMRC website here. HMRC will also post you a paper tax return if requested.