INTM860230 | Diplomatic Missions: exemptions from Income Tax
From HM Revenue & Customs · International Manual
Exemptions from Income Tax on the ground of diplomatic privilege apply to
the official emoluments of members of the mission (INTM860210) and to emoluments which their private servants receive as servants of members of the mission
private income from outside the United Kingdom of the head of mission, members of the diplomatic staff of the mission and members of the administrative and technical staff of the mission. The exemption applies even if the income is payable in or remitted to the United Kingdom.
The exemption does not apply to private income from outside the United Kingdom of
members of the service staff of the mission or their families, or
private servants of members of the mission or their families.
The diplomatic privilege exemption does not apply in any case to private income arising from sources within the United Kingdom. "Private income from sources within the United Kingdom" would include the salary paid to the family member of a diplomat where the family member works in the UK remotely for a non-UK employer, even if the revenue is generated outside the UK.
If you get a claim to exemption from a member of the family forming part of the household of a person entitled to the exemption refer it to BAI, Business International (Immunities & Privileges).