SA103S or SA103F: Which Self-Employment Form Do You Need?

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If you are self-employed in the UK and complete a Self Assessment tax return, you may come across two forms called SA103S and SA103F. Both are used to report self-employed income and expenses to HMRC, but they are designed for different types of businesses.

The names can make them sound more complicated than they really are. SA103S is simply the short version of the self-employment pages, while SA103F is the full version used when more information about the business is required.

What is the SA103S form?

The SA103S is the Self Assessment Self-employment (short) form.

It is a supplementary part of the main SA100 Self Assessment tax return and is used to tell HMRC about income and expenses from working for yourself as a sole trader.

For the 2025/26 tax year, you can normally use SA103S if your annual business turnover was less than £90,000, provided your tax affairs are straightforward enough to use the short form.

Turnover means the total amount your business received or earned before expenses are deducted. For example, if customers paid you £65,000 during the year and you had £20,000 of allowable business expenses, your turnover would still be £65,000, not £45,000.

The SA103S asks for information such as your type of business, turnover, allowable business expenses, taxable profit or loss, capital allowances and any CIS tax deducted if you work as a subcontractor in the construction industry.

If you are unsure what costs can be deducted from your income, you can read my guide on what self-employed expenses you can claim.

The short form is suitable for many sole traders with relatively simple businesses because HMRC does not need the same level of detail that is required on the full SA103F form.

It is also worth remembering that the £90,000 test is based on what your turnover would have been if you had traded for a full year. This can matter if you only started your business part way through the tax year.

If you have more than one separate self-employed business, additional rules apply because each trade generally needs to be reported separately.

What is the SA103F form?

The SA103F is the Self Assessment Self-employment (full) form.

It performs the same basic job as SA103S because it reports your self-employed business income and calculates the profit or loss that needs to be included on your Self Assessment tax return, but it asks for considerably more information.

For the 2025/26 tax year, you will normally need the full SA103F pages if your business turnover was £90,000 or more, or would have been £90,000 or more if you had traded for the full year.

However, turnover is not the only reason why you may need SA103F. HMRC also requires the full pages in a number of situations where your business or tax calculation is more complicated.

The full form contains additional sections covering matters such as detailed business expenses, capital allowances, losses, adjustments to taxable profits and other information that HMRC may need to calculate your tax correctly.

For example, instead of simply giving HMRC a smaller number of expense totals, the full pages provide space for a more detailed breakdown of your business costs.

This does not mean that someone completing SA103F necessarily pays more tax. The form is simply designed to collect more information.

If you are trying to understand the wider Self Assessment process rather than just the self-employment pages, my guide on doing your own Self Assessment tax return explains how the return works and what information you normally need.

You should also check the SA103F rules carefully even when your turnover is below £90,000, because certain circumstances can still mean that the full pages are required.

What is the difference between SA103F and SA103S?

The main difference between SA103S and SA103F is the amount of information HMRC requires about your self-employed business.

SA103S means Self-employment (short) and is designed for smaller and relatively straightforward businesses. SA103F means Self-employment (full) and is used for larger businesses and situations where HMRC needs more detailed information.

For the 2025/26 tax year, the basic distinction looks like this:

	SA103S	SA103F
Form	Self-employment (short)	Self-employment (full)
Used for	Simpler self-employment	Larger or more complicated self-employment
Turnover	Normally below £90,000	Normally £90,000 or more
Business income	Yes	Yes
Business expenses	Yes	Yes, with more detail
Profit or loss	Yes	Yes
Capital allowances	Basic information	More detailed information
CIS deductions	Can be reported	Can be reported
Part of Self Assessment	Yes	Yes

A common mistake is to think that SA103S and SA103F are two completely different tax returns. They are not.

Your main individual tax return is normally the SA100, while SA103S or SA103F are supplementary self-employment pages that provide HMRC with information about your business.

For example, someone who is employed during the week but also runs a self-employed business at weekends may need to report their PAYE employment income and then complete the relevant self-employment pages for their business.

Which version you need depends mainly on the size and complexity of the self-employment.

If you are just starting to deal with Self Assessment, you may also find my guide to the self-employed tax forms used in the UK useful, as there are several different forms and supplementary pages depending on the type of income you receive.

One final point is that these form numbers are most noticeable when dealing with paper tax returns or looking at HMRC forms and guidance. If you submit your return using online tax software, you may not physically see a form called SA103S or SA103F because the software normally asks questions and completes the appropriate parts of the tax return in the background.

The important thing is therefore not simply choosing the form with fewer boxes, but making sure that HMRC receives all the information required for your particular self-employed business.

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