SolvedSW01300 | Introduction: Service Availability
From HM Revenue & Customs · Shared Workspace Business Manual
Shared Workspace is normally available 24 hours a day, 365 days a year.
Planned downtime will be kept to a minimum, and wherever possible outside the business hours of 08:00 to 18:00.
Advanced details of any planned downtime is available through the Shared Workspace pages of the HMRC website.