The poll tax was first levied in 1377, and again in 1379 and once more two years later, with a basis that was a little different in each case. Initially everyone 14 and over had to pay 4d (2p). By 1379 that had become graded according to social class over the age of 16, and by 1381, it was everyone over 15 (the poor were exempt). It was not re-imposed after the Peasants’ Revolt of 1381. The next general poll tax was levied in 1513, and it was imposed again six times between 1641 and 1698. In 1694, 1695 and twice in 1698 it was imposed to pay off the debts and arrears of the army and navy. Payment by then was graduated at the rate of 6 shillings and upwards according to rank and means; only the poor and children under 16 were exempt. The collectors of the poll tax faced similar difficulties to those of the hearth tax and the records are incomplete. 1698 was the last year of collection.

That makes it an excellent record of the population, if the records for your area still exist. Even the older records from the 1300s list people by name, making these quite the fullest medieval documents, and the ones where you're most likely to catch a glimpse of an ancestor.