Tax rules can change between tax years. Use this guide to choose between 2024/25, 2025/26, and 2026/27 and understand why the same profit can produce different results.
A tax-year label is not just a UI detail. The calculator loads a specific set of rates for that year. If you choose the wrong year, the estimate may look “wrong” even if your profit input is correct.
Use the year you are filing for (or the year you are planning for). If you are forecasting forward, you can compare 2024/25, 2025/26, and 2026/27 to see how rate changes affect your plan.
If you are unsure which year applies, treat this as a planning estimate and confirm your filing year using official guidance. Avoid making decisions based on a single year’s result without checking that it matches your situation.
Not tax advice. This guide is intended to reduce input errors and improve planning.
Last updated: 2026-04-20
Because the calculator uses different rate files by tax year, and those rules can change.
Not necessarily. Pick the year you are filing for or planning for, then use other years only as sensitivity checks.
Yes. Region affects the Income Tax bands used by the estimate, so choose the correct region as well.
For official rules and definitions, verify with the references below.