The Tithe Commutation Act 1836 aimed to change payments of tithe (a tax to support the church) which had traditionally been taken as payments in kind e.g. so many bushels of wheat or so many livestock, to money payments in the form of a tithe rent charge. These tithe apportionments were created to record liability to pay tithe rentcharge. 11,830 tithe districts were apportioned and mapped: 10,871 in England and 959 in Wales. The apportionments generally set out the names of the holders and occupiers of land in each tithe district (usually a parish or township), the acreage and use of each parcel of land, the amount of tithe rentcharge payable and the names of the tithe owners. Until 1936, subsequent altered apportionments were added after the original apportionments.
Tithe Apportionments, 1836-1929 [database online]. TheGenealogist.co.uk 2017
Original data: "IR29 Tithe Commission and successors: Tithe Apportionments" The National Archives