Late Filing & Underpayment Penalties: What Do I Owe?

You missed the deadline and now you want to know the damage before HMRC tells you. Give it your submission date, the tax owed and when you paid, and it works through the £100 penalty, any daily charges, the 5% surcharges at 30 days, 6 and 12 months, and the interest. A clear figure instead of a vague dread.

I missed the UK Self-Assessment deadline. Here are the facts: Return submission date: {SUBMISSION_DATE}. Tax owed: £{TAX_OWED}. Date tax was (or will be) paid: {PAYMENT_DATE}. Calculate and explain in detail: (1) the automatic £100 late filing penalty, (2) any additional daily penalties if applicable, (3) the 5% surcharges on unpaid tax at the 30-day, 6-month, and 12-month thresholds, (4) interest on the unpaid tax at HMRC's current rate, and (5) the total amount I now owe beyond the original tax bill. Also explain whether I have grounds to appeal any penalties using the 'reasonable excuse' provisions, and how I would make that appeal.