The five checks worth doing before you press submit
- Use Side Hustle and Self Assessment Checker if you are still not sure whether HMRC expects the return at all.
- Re-check Adjusted Net Income if Gift Aid, pension top-ups or family support thresholds are involved.
- Use CGT on shares if disposals outside wrappers are part of the return.
- Use Sole Trader Tax Estimator if the pressure point is profit, reserves or balancing-payment cashflow.
- Check the official deadline page on GOV.UK for the final filing and payment dates.
Official deadline anchor
GOV.UK's Self Assessment deadline page is the source of truth for the online filing deadline, balancing payment and first payment on account date. Use the site tools to sense-check your numbers, then file using HMRC's own system or your accountant's process.