• Son of William Duncan, wright, Aberdeen.
• 1765 – 69 – Educated Kings College.
• Apprenticed to John Alexander.
• 1768 – Joint Trades Clerk to the Incorporated Trades of Aberdeen, 15th November
• At a meeting of the Convener Court on the 15 November 1768, Thomas Duncan and David Morrice Jnr being called on appeared and declared they would be willing to serve the Trades and to accept the said office and accordingly gave their oath, thereafter signed the Minute book
• Sheriff Substitute of Aberdeenshire.
• 1777 – Married to Elizabeth Johnston
• 1795 – It was noted in the minutes of 30 May 1795 that following the death of Mr David Morrice , his joint Clerk Thomas Duncan intimated his resignation as Clerk and therefore the position of joint Clerks and Assessors would have to be filled. The resignation was accepted by the Convener Court and a Clerk pro tempore be appointed in order that the appointment of new Clerks could be carried out. Dr Arthur Dingwall Fordyce was appointed to this position.
• 1816 – Died.