Self Assessment is how self-employed people report their income to HMRC. This guide explains it in simple terms and how CabTax can help you prepare.
Self Assessment is the form (SA100) you use to tell HMRC about your income and expenses for the tax year, so they can work out your tax.
You usually need to do a Self Assessment if you are self-employed, a sole trader earning over £1,000, or have untaxed income like rental income or large savings interest.
For the 2025-26 tax year, the online deadline is 31 January 2027. Paper returns are due by 31 October 2026.
Records of all your income and allowable expenses. CabTax keeps these for you and can export a summary.
CabTax lets you log income and expenses through the year, gives you a live tax estimate, and exports an SA100 summary to help you complete your return.
Join the waiting list and we'll email you the moment it's live — log income, expenses and mileage, and see your tax estimate as you go.
Join the waiting list and be first through the door.