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What is SA100 tax return?
Last verified 23 October 2026
The SA100 is HMRC's main Self Assessment tax return. You use it to report your income, claim reliefs and ask for any repayment due, adding supplementary pages for particular types of income.
Why it matters to landlords
Landlords add SA105 for UK property income and SA106 for foreign income, including overseas rent. Other common pages include SA102 for employment, SA103 for self-employment and SA108 for capital gains. The current version covers the tax year 6 April 2025 to 5 April 2026.
You can file on paper, which must reach HMRC by 31 October after the tax year, or online by 31 January. Filing online gives you longer, lets you save and finish later and makes amendments easier. Once you join Making Tax Digital for Income Tax, you submit your tax return through your compatible software rather than through GOV.UK, adding your other income and making the declaration there. If you are exempt, you keep filing a Self Assessment return as before.
Example
A teacher with two buy to let houses and no MTD obligation yet files the SA100 with SA102 for their salary and SA105 for the rental income, online by 31 January.
How to submit your tax return digitally →
Related terms
- SA105 (UK property pages)
- Self Assessment
- Self Assessment deadlines
- Final declaration
- Unique Taxpayer Reference (UTR)