The four letterbooks that have survived contain 1,116 retained copies of Tailyour's letters. His early letter books (1781-1785) detail his initial struggles in America, when he first tried his hand at general trade, and later attempted to provide supplies for British prisoners-of-war after the American Revolution. Both attempts failed, and by 1782, he started thinking about moving to Jamaica to work with his cousin Simon Taylor. During this time, Tailyour kept in touch with his British contacts, including George McCall, the Andersons, and his brother Hercules, whom he hoped to recruit for the American trade.
John Tailyour started his career in Kingston, Jamaica, as a trader in dry goods and sundry stores, but soon added the purchase and sale of slaves to his business. Many of his letters after 1783 focus on the condition of the slave trade and the threat from abolitionists in England. Tailyour styled himself as an expert slave trader, able to sell entire ships of slaves quickly. Much of his correspondence about the trade focuses on the kinds of issues that affected its viability, including the health of the slaves, the health of the markets, the age and sex of the slaves, and the locations of sale.
Tailyour wrote many letters about the abolitionist threat as well, and the damage he anticipated from abolition. Contrary to some accounts, Tailyour's reports on the slave trade indicate that it was robust at the end of the eighteenth century. Though he foresaw a potentially large loss of business if the trade were outlawed, Tailyour did not reflect much on the social effects of this, but he did note in 1788 that "from all the best information I ever had, it clearly appears Slaves live better by far in the West Indies than in Africa, & from my own observations I can say they in general live better than the Poor of Scotland, Ireland & probably England."
Toward the end of his life, Tailyour wrote more directly about issues concerning his health, his estate in Scotland, and the business news from his correspondents.