A simple overview of registering for Self Assessment and what information you typically need, with official links.
Many people use a calculator for planning before registering. Registration is the formal step that tells HMRC you need to complete Self Assessment.
Before you start, note when you started trading, your rough income and costs, and any other income sources. This reduces rework later.
Use the calculator to estimate tax and National Insurance from profit. This site does not submit anything to HMRC.
Not tax advice. This page is an educational guide. For official rules, verify the sources below.
Last updated: 2026-04-20
Yes. It is for planning and does not require an account.
No. Registration is done on GOV.UK.
Use GOV.UK guidance and, if unsure, ask a professional.
For official rules and definitions, verify with the references below.