Jaffrey joined the North of Scotland Bank in 1877 and in 1892 was appointed actuary of the Aberdeen Savings Bank, a post he held for 37 years. After his retirement he served as the bank's consulting actuary until his death.
He was Lord Rector's Assessor in the Court of the University of Aberdeen from 1924 to 1937, chairman of the Aberdeen Art Gallery Committee and the Aberdeen branch of the Royal Horticultural Society. He founded the Jaffrey Chair of Political Economy at the university.
- The London Gazette: . 30 December 1919.
- Obituary, The Times, 25 July 1953