Key dates (tax year ending 5 Apr 2027)
5 Oct 2026 Registration deadline First-time filers must register with HMRC by this date
31 Oct 2026 Paper return deadline Online filing extends this — paper-only cut-off
31 Jan 2027 Online return + balancing payment Plus first payment on account, if applicable
31 Jul 2027 Second payment on account For 2026/27 tax year, if payments on account apply
Late-filing penalty escalation
Day 1 late £100
3 months late +£10/day
6 months late +5% or £300
12 months late +5% or £300