Kinnaird was partner in the banking firm of Ransom, Morland and Hammersley of Pall Mall, London; the MP William Morland was one of the partners, as was Hugh Hammersley MP.
In politics Kinnaird acted as treasurer to the Society of the Friends of the People, which he joined in 1792 with James Maitland, 8th Earl of Lauderdale and David Erskine, 11th Earl of Buchan [REF].