HM Revenue and Customs does not allow extra time in the event of a customer's computer system failing. There is a variety of payment methods available which do not rely on computer access. Customers are notified in advance of the date(s) that payment is due. It is the customer's responsibility to ensure payment reaches HMRC on time. There is full “how to pay” guidance relating to all, and this sets out the various methods of payment requests and reminders issued by HMRC.