UK households warned 'double' HMRC deadline with £100 penalty warningThe deadlines are set for October with the penalties going up to £1,600 for those that delayView Image UK households have been warned of two HMRC deadlines (Image: Getty Images)UK households have been warned of two HMRC deadlines that, if they are missed, could see them face a £100 penalty. ‌October 5 is the self-assessment registration cut-off date, while October 31 is the paper return deadline. "If you register late, your filing deadline is extended to three months from when HMRC issues a return or notice. ‌The finance expert warned that late filing penalties can escalate, "if a return is more than three months late, daily penalties of £10 apply, up to £900." "HMRC may consider appeals against late filing penalties, but only after the return has been filed.