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How to complete the SA103 self-employment tax return form

The SA103 form is the document you need to complete so you can pay tax on income from self-employment.

There are two kinds of SA103:

  • the short version, called SA103S, which can be used by most self-employed people
  • the “full version”, called SA103F, which is used by sole traders with more complex situations (they earn over the VAT limit, are a practising barrister, use traditional accounting instead of the usual cash basis, etc.)

How do I know if I’m self-employed?

It’s not always as easy as it sounds:

  • Are you working with a full-time employment contract? Then you’re not self-employed
  • Are you using a limited company to do business? Then you’re an employee of your own company (or an umbrella company), but not self-employed.

Also, in case you’re wondering: “sole trader” is the same as “self-employed”.

How do I fill it in?

You can get the “shorter” SA103S form from this HMRC page:

  1. select the year that you need the form for
  2. download the SA103S pdf
  3. print it, fill it in, and send it to HMRC via post

If you file a Self Assessment tax return every year, then HMRC might also send it to you.

In any case, make sure you first read the “Self-employment (notes)” pdf for that tax year – it’s on the same HMRC page.

It will explain what each line item on the form means, and how to fill it.

If you want the full version, download the SA103F form here instead.

How do I submit it?

You need to send it together with your SA100 form (the main tax return form) – you can’t file the SA103 by itself.

Can I send it to HMRC online?

No, you need to send it by post.

The good news is that you can choose to do your entire Self Assessment online. Plus you can get another 3 months to do it since the deadline for sending the paper form is October 31st, but for online tax returns is 3 months later (end of January).

At TaxScouts we can file your tax return online for you instead – and for a flat £119, regardless of how many sources of income you have or what kind of self-employed you are.

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