HMRC is about to charge you £10/day. Yes, really.

Starting 1 March 2026, HMRC charges £10/day on top of the initial £100 late-filing penalty for overdue self-assessment tax returns, potentially reaching £1,000+ within months. Filers can submit estimated figures immediately to stop the daily penalty clock and amend later, as HMRC prefers a rough return over continued non-filing. Reasonable excuses for appeals are narrow, and Time to Pay arrangements are available for those who cannot pay.