If the employee is sufficiently unwell that they are not capable of work, they should of course be treated as on sick leave and would be entitled to SSP (and potentially company sick pay, if applicable). If the employee is well enough to work, but is unable to work due to the self-isolation requirement (i.e. if remote working from abroad is not possible, or is not permitted by the employer), they would be deemed to be incapable of work and therefore entitled to SSP for 11 days starting on the earlier of the date the employee started showing symptoms or the date the test was taken. If symptoms continue beyond those 11 days, SSP entitlement is extended accordingly. (The employee may potentially also be entitled to company sick pay, if applicable.)