Self Assessment deadlines: what should I check?

A practical checklist for common Self Assessment deadlines and where to confirm the latest dates on GOV.UK.

Use this as a checklist, then confirm the current deadlines on GOV.UK.
Plan backward from the deadline: records, profit estimate, and payment planning.
If you miss a deadline, do not guess; verify options and next steps on official guidance.

What this page is for

Deadlines are a common source of anxiety for first-time filers. This guide helps you understand which dates matter and where to confirm the latest information. It avoids hard-coding dates so you can always check the current position.

How to use this with the calculator

Run the calculator to estimate an annual total, then use that estimate to plan cash flow and avoid surprises. The tool does not decide what you must file; it helps you plan.

Common mistakes

Relying on a random blog post for dates, mixing up filing and payment steps, and leaving everything to the last minute. Use GOV.UK as the source of truth.

Not tax advice. This page is an educational guide. For official rules, verify the sources below.

Open self-employed calculator How this is maintained

Last updated: 2026-04-20

FAQ

Do you show the exact dates here?

No. Dates can change. We link to GOV.UK so you can confirm the current deadlines.

Is this calculator a filing service?

No. It is a browser-based estimate tool to help you plan.

What if my situation is complex?

Use this as a starting point and verify the official guidance. Consider professional help if you are unsure.

Sources

For official rules and definitions, verify with the references below.

https://www.gov.uk/self-assessment-tax-returns/deadlines