Self Assessment Penalty Calculator 2025/26
Calculate exactly how much HMRC will charge you for a late self assessment return and late tax payment, including the £100 initial penalty, daily charges, 6-month and 12-month surcharges, and daily interest on unpaid tax.
HMRC self assessment penalty structure
Missing the 31 January online filing deadline triggers an automatic £100 penalty — even if you owe no tax. After 3 months, daily penalties of £10/day kick in for up to 90 days (maximum £900). After 6 months, a further penalty of 5% of the tax due (or £300, whichever is higher) is charged. After 12 months, another 5% (or £300) penalty applies, with higher rates possible in serious cases.
Late payment interest is charged at the Bank of England base rate plus 2.5% — currently around 7% per annum (as of early 2025). A 5% surcharge also applies to unpaid tax after 30 days, 6 months, and 12 months.
31 October 2025: Paper return deadline · 31 January 2026: Online return & payment deadline · 31 July 2026: Payment on account (2nd instalment)
