The Poll Tax was a flat rate tax. It was not based on ability to pay. Everyone over eighteen was liable. Rich and poor paid the same. The millionaire paid the same as the toilet attendant. The lawyer paid the same as the shop assistant. The Prime Minister Margaret Thatcher and her multi-millionaire husband paid the same as their gardener.
The tax, officially called the Community Charge, was dubbed the Poll Tax because of its similarity to a tax introduced in 1381. That tax was so disliked it provoked the peasants' revolt. The government tried to counter this analogy, but the name stuck.