O.H.M.S.

From Wikipedia, the free encyclopedia

O.H.M.S. (On Her Majesty's Service or when the monarch is male, On His Majesty's Service) is an endorsement commonly seen on official correspondence from government departments in Commonwealth Realms.

In Canada, you may write O.H.M.S on an envelope instead of using postage stamps for any letters being sent to the House of Commons or to any member of the Canadian Parliament.