Selective Employment Tax
SET was intended to subsidise manufacturing industry from the proceeds of the services industries, to help exports. At the end of each accounting period, manufacturing companies would have their SET payments refunded, along with a 7s 6d bounty per employee.
SET was designed to be a tax on those companies that did not help UK exports. UK High Street Bookmakers used the introduction of this tax as a reason to reduce the payout on some Each Way bets - where a horse is placed in the first two or three, depending on the number of runners - from a quarter the odds to a fifth the odds. When the tax ended, the older, larger payouts were never restored.
This tax was introduced during the first Wilson ministry in 1966 with the Selective Employment Payments Act 1966. It was dropped in favour of the introduction of VAT by the Heath ministry of 1970-1974.