[2] His father, an Oxford man, came to Ireland as an army chaplain with William III of England, and settled in Ulster.
[3] William's mother was the daughter of John McNeill of Ballintoy, County Antrim, and Elizabeth Ruthven, widow of Sir Dugald Stewart, 2nd Baronet, and thus though her mother a half-sister of James Stuart, 1st Earl of Bute.
[4] He went to school in Raphoe and attended Trinity College Dublin, graduating in 1727.
[5] In 1759 he was made a Puisne Justice of the Court of King's Bench (Ireland),[6] and on 1 August 1768 he was transferred to the Court of Exchequer (Ireland) as a Puisne Baron.
On 13 December 1771 Scott and fellow Barons of the Exchequer Foster and Smyth, along with the Lord Chancellor Lifford and the Chancellor of the Exchequer Hamilton, were appointed Commissioners of Accounts for Ireland by Letters Patent.