This hub is built to get you to a usable Self Assessment estimate without mixing up turnover, profit, NIC settings, student loan, or pension inputs. Start with the calculator only if you already know your annual profit after allowable expenses.
Start from the number or edge case you already understand.
Pick the fastest route based on the input you have ready today.
Guides clarify inputs and limitations. “Entry” pages are common search phrases that lead into the same calculator.
If you're unsure what to enter (profit vs turnover, expenses), start here.
Understand why National Insurance appears separately and what inputs drive it (simplified).
Reduce input errors: confirm your plan and understand how repayments fit into the estimate.
Use pension inputs safely: understand limitations and avoid over-trusting simplified relief logic.
Pick the right tax year and region in the calculator so the estimate uses the correct rate file.
Turn an annual estimate into a repeatable set-aside habit.
Additional self-employed pages in this cluster.
For official rules and definitions, verify with the references below.
Last updated: 2026-04-20