Free UK Tax Penalty Calculator 2026 – Estimate Your HMRC Fines

Find out how much you could owe in tax penalties for late filing, late payment, or inaccuracies on your Self Assessment. Our free UK tax penalty calculator gives you an estimate based on the latest 2026 HMRC rules, so you can plan ahead and avoid surprises.

Home / UK Tax Penalty Calculator 2026 – Estimate HMRC Fines & Surcharges

⚠️ Penalty Calculator UK 2026 🇬🇧 HMRC estimates

The penalty is calculated as a % of this amount
A late filing penalty can be increased if a notice was issued
⚠️ Disclaimer: This calculator provides estimates based on HMRC penalty rules for the 2026 tax year. It does not constitute professional advice. Actual penalties depend on individual circumstances, behaviour, and HMRC's assessment. For accurate computation, contact our accountant or place an order for specialist advice tailored to your situation.
2026 tax year · Penalty rules: FA 2008, Schedule 41 · Updated for 2026/27