HMRC to fine UK households £1,600 and could 'initiate court proceedings'Self Assessment taxpayers are being reminded by HMRC of two important deadlines in October 2025. View Image HMRC to fine UK households £1,600 and could 'initiate court proceedings'HMRC has warned UK households could be hit with a £1,600 tax fine - as a double deadline looms. Self Assessment taxpayers are being reminded by HMRC of two important deadlines in October 2025. George Holmes, managing director of Aurora Capital, said: "Under the old Self Assessment rules, a late filing meant an immediate £100 fine. You’ll need to keep records (for example bank statements or receipts) so you can fill in your tax return correctly.