What Is the SA100 Tax Form
The SA100 is the main Self Assessment tax form used to report untaxed income in the UK. If you’re self-employed, earn rental income, receive dividends or pensions, or have made gains on asset sales, you’ll likely need to complete it. The form allows HMRC to calculate how much tax you owe — or are due back.
Who Needs to Complete an SA100?
You’ll need to complete an SA100 form if you receive income that isn’t fully taxed through PAYE. This includes:
- Self-employed individuals
- Company directors with untaxed income
- Employees earning tips or commissions
- Landlords with rental or holiday let income
- UK residents earning from overseas
- Individuals with capital gains (from property, shares, etc.)
- Side business owners or freelancers
- High earners (£100,000+ per year)
If HMRC has issued you a notice to file a return, or you know you have untaxed income, it’s your responsibility to complete the form.
What Does the SA100 Form Cover?
The SA100 form gathers information across several sections:
- Personal information – Your name, NI number, and tax reference
- Income details – Including interest, dividends, pensions, and benefits
- Reliefs and deductions – Such as Gift Aid or pension contributions
- Student loans and child benefit charges
- Overpayments or tax owed
- Tax adviser information, if applicable
Depending on your situation, you may also need to complete supplementary pages, like SA105 (UK property), SA103 (self-employment), or SA108 (Capital Gains).
How to Fill Out the SA100
- Get your paperwork together – P60s, P11Ds, income statements, expense records, pension details.
- Choose how to file – Online is faster and gives you more time (31 Jan deadline), while paper returns are due earlier (31 Oct).
- Work through each section – Declare all sources of income and eligible tax reliefs.
- Add any extra pages – For property, gains, foreign income, etc.
- Double-check your entries – Mistakes can lead to fines.
- Submit on time – Use your Government Gateway ID to file online or request a paper form from HMRC.
If your income is over £50,000 and you or your partner claim Child Benefit, you must also complete the High Income Child Benefit Charge section.
SA100 Deadlines
To avoid late penalties:
- Paper returns: Submit by 31 October
- Online returns: Submit by 31 January
- For PAYE collection: Submit by 30 December
Let Easy Accounting Services Handle It for You
Completing the SA100 can be time-consuming — especially if you have multiple income sources or additional forms to file. At Easy Accounting Services, we take the stress out of tax season.
Our Self Assessment specialists ensure every detail is correct, deadlines are met, and no tax-saving opportunity is missed. Whether you need help completing the SA100 or advice on Capital Gains Tax, we’re here to support you.
FAQs
How do I access the SA100 form?
Log in via your Government Gateway account to complete it online, or request a paper form by contacting HMRC.
Can I download a blank SA100 form?
You can only download a reference copy. To submit a real return, you must use HMRC’s online system or request an official paper form.
What does the SA100 form look like?
It’s an eight-page document marked with “SA100” and the relevant tax year (e.g., SA100 2025), listing all income and tax relief details.
