In common historic and modern usage, a hearth is a brick- or stone-lined fireplace or oven used for cooking and/or heating. Because of its nature, in historic times the hearth was considered an integral part of a home, often its central or most important feature. This concept has been generalized to refer to a homeplace or household, as in the terms "hearth and home" and "keep the home fires burning." In fireplace design, the hearth is often considered the visible elements of the fireplace, with emphasis upon the floor level extension of masonry associated with the base of the firebox.
Lined hearths are easily identified by the presence of fire-cracked rock, often created when the heat from the fires inside the hearths chemically altered and cracked the stone. Often present are fragmented fish and animal bones, carbonized shell, charcoal, ash, and other waste products, all imbedded in a matrix of soil that has been deposited atop the hearth. Unlined hearths, which are less easily identified, may also include these materials. Because of the organic nature of most of these items, they can be used to pinpoint the date the hearth was last used via the process of radiocarbon dating. Although carbon dates can be negatively affected if the prehistoric users of the hearth burned old wood or coal, the process is typically quite reliable.
A revision of the Act in 1664 made the tax payable by all who had more than two chimneys
The tax was abolished by William III in 1689 and the last collection was for Lady Day of that year. It was abolished in Scotland in 1690.
Hearth tax records are impotant to local historians as they provide an indication of the size of each assessed house at the time. The numbers of hearths are generally proportional to the size of the house. The assessments can be used to indicate the numbers and local distribution of larger and smaller houses. Not every room had a hearth, and not all houses of the same size had exactly the same number of hearths, so they are not an exact measure of house size.
Published lists are available of many returns and the original documents are in the Public Record Office. The most informative returns, many of which have been published, occur between 1662-1666 and 1669-1674.