What is an SA100 form?

What is SA100? To put it simply, an ‘SA100 form’ is the official name for your self-assessment tax return. Today, SimpleTax is going back to basics, telling you everything you need to know about the SA100…

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Last Updated: 6th January 2023

What is SA100?

To put it simply, an ‘SA100 form’ is the official name for your self-assessment tax return. Today, SimpleTax is going back to basics, telling you everything you need to know about the SA100 tax form, in an easy to understand SA100 Guide.

Who needs an SA100?

You must submit an SA100 form (tax return) if you’re:

  • Self-employed
  • A company director, minister, Lloyd’s name or member
  • Receiving an annual income of £100,000 or more
  • Receiving income from savings, investment or property
  • Planning to claim expenses or reliefs
  • Receiving child benefit and income is above £50,000
  • Receiving foreign income
  • Paying capital gains tax
  • A trustee.

Alternatively, if you’re still unsure on how to fill in an sa100 form or whether you need to fill one out at all, you can ask the SimpleTax Wizard. Our wizardry friend will ask you 8 simple yes or no questions and in minutes, you’ll know whether you need to file an sa100 tax return or not. Easy peasy!

Where can I find an SA100 form?

You can decide whether you would like to submit your SA100 form by paper or online. Online is by far, the easiest and quickest way to file your tax return, especially if you choose to use SimpleTax.

Online – sending your tax return online is much easier, and beats printing pages and pages of supplementary pages; all you need to do is create an account with SimpleTax, add your income and expense details and click submit. Our intelligent software will sift through pages and pages of information for you, whilst instantly updating all calculations. Make a hard job easy; Go SimpleTax.

Paper – If for some reason, you would still prefer to file your SA100 form by paper, then this is an option too. You can download the SA100 form via HMRC’s website, but remember to apply for your UTR at least 6 weeks before the tax deadline; without a UTR you will not be able to submit a tax return, and this will result in a penalty. But don’t worry, you can apply for your UTR via the SimpleTax Wizard, in minutes.

If you’re wondering where to send your SA100 form, then the below address is appropriate if you haven’t had any recent correspondence with HMRC:

Pay As You Earn and Self Assessment

HM Revenue & Customs


When must I submit an SA100 form?

The deadline for paper tax returns is 31st October each year. If you choose to submit your SA100 with SimpleTax, not only is it, well, super simple; but you also get an extra 3 months! HOORAY. Yes, the deadline for online self-assessment tax returns (SA100) is 31st January.

So, hopefully, our sa100 notes have cleared up any confusion surrounding this area of self-assessment. Besides, there’s no need to be confused because SimpleTax makes tax super simple. Take the hassle-free route to filing your taxes; Go SimpleTax.

View our Guide to Self Assessment Tax Returns

SA100 Frequently Asked Questions

  • What is a SA100?

    It’s the official name for your HMRC self assessment tax return form

  • Who needs an SA100?

    Anyone who needs to complete an UK tax return will need to complete this. It can be done either online or via a PDF form that can be downloaded from the HMRC website

  • Can I Complete The SA100 Form Online?

    You can complete the form online via the HMRC website or using a tool such as GoSimpleTax

  • How Do I Download a SA100 Form?

    You can download a PDF form from the HMRC website which can then be completed on your computer and printed off

  • What’s the due date for online completions of the SA100?

    For the 2021 / 2022 tax year the due date for online completions is 31st January 2023.

  • What’s the due date for paper completions of the SA100

    For the 2021 / 2022 tax year the due date for paper completions is 31st October 2022.

  • What’s the Difference Between an SA100 and SA302?

    The SA100 is the HMRC UK tax return document that needs to completed by anyone required to complete a self assessment tax return. The SA302 is a statement given by HMRC that provides evidence of your earnings

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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.

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