How is claiming Overseas Workday Relief viewed by the UK tax authorities?
The relief (which applies to the majority of employees moving to the UK who work internationally) is clearly set out in the UK tax law and is intended to encourage internationally mobile employees to come to the UK.
How do holidays/ sick days/ public holidays count for Overseas Workday Relief purposes?
HMRC guidance is limited in this area, merely emphasizing that Overseas Workday Relief should be calculated on “a just and reasonable basis”. This means that HMRC expect apportionment by workdays instead of calendar days. The UK workday ratio is calculated according to days actually worked. Any days an employee doesn’t work because they’re sick or on leave are not workdays.
If you do personally work on weekends or public holidays, these days should be counted, but you should ensure the records are retained to evidence the fact that you worked.