Jackson was still serving at the Cape in 1797, by then having taken responsibility as a navy agent for prize money on the station.
He often worked in partnership with the insurance broker John Petty Muspratt, and continued as a merchant in Broad Street for the rest of his life.
In 1803 Jackson put himself forward as a candidate to fill an empty seat on the court of directors of the East India Company (EIC), citing his previous experiences, but later withdrew.
At the 1807 United Kingdom general election he stood to be returned for Dover, being opposed by two supporters of the Second Portland ministry.
Jackson won the second of the two seats available for Dover, being beaten out by Charles Jenkinson by only six votes in a poll of over 1,200 people.