A successful London banker. Son of John Coutts (1699-1750), Lord Provost of Edinburgh (1742-44), and Jean Stewart. Brother of James Coutts. Married twice, first to Susan or Elizabeth Starkie (d. 1815) and later to actress Harriet Mellon (d. 1837).
As a young man, he became a partner in Coutts Brothers & Co. (with his brothers James, John and Patrick). In 1761 he joined his brother James in London in a banking firm which then became James & Thomas Coutts. Pottle mentions that James Coutts, by 1776, "had been virtually insane for some years and had been bought out by Thomas in 1775". (BOY, p. 309) At the same time, the firm changed its name to Thomas Coutts & Co, under which it was known until his death in 1822.
Under Thomas' directorship, the bank got as its customers many important people including reigning monarchs and important politicians (Including sometime PM William Pitt the Younger).1 It seems that even composer Ludwig van Beethoven sometimes made use of the company's services.2
It later became known as Coutts & Co., which exists to this day as a part of the NatWest group.
Boswell used the Coutts' as bankers and saw a bit of both (although apparently most of James) during his 1762-3 stay in London. On May 28, 1763, he describes Thomas Coutts as "a very good fellow [who] has a great deal of little humour and fun."
E. H. Coleridge's 2 volume biography The Life of Thomas Coutts, Banker was published ca. 1920 and is often available from used bookstores via AbeBooks.