An Inquisition post mortem (abbreviated to Inq.p.m. or i.p.m., and formerly known as an escheat) (Latin, meaning "(inquisition) after death") is an English medieval record of the death, estate and heir of one of the king's tenants-in-chief, made for royal fiscal purposes. The process of making such inquisition was effected by the royal escheators in each county where the deceased held land. The earliest inq.p.m. was made in 1236, in the reign of King Henry III (1216–1272), and the practice ceased c.1640, at the start of the Civil War, and was finally abolished by the Tenures Abolition Act 1660, which ended the feudal system.
The escheators were ordered by a writ from the king's chancery to investigate the deaths of tenants-in-chief in order to assess what monetary value was due to the king from his so-called feudal incidents, comprising for example feudal relief, wardships, and marriages. Such revenues which resulted from the deaths of his tenants-in-chief formed a significant proportion of the mediaeval royal revenues. The feudal due which was payable to the king on the inheritance of the lands by the tenant's heir is termed a relief, from Latin levo, levare (to lift-up), plus re (again), signifying the process of re-elevating the heir to the honourable position of the deceased, as a lord of the manor and tenant-in-chief. The scale of reliefs payable to the king by his tenants-in-chief who held under the feudal land tenure of barony had become a fixed sum under clause two of Magna Carta (1215), but the king nevertheless needed to know who the heir was so payment of the relief could be demanded. If the tenant-in-chief was found to have no heir, for example if he was unmarried or childless, the lands held would "escheat" (i.e. revert to the demesne of the king) to be re-granted as a valuable reward to a favoured courtier or official, or sold for cash proceeds. This aspect of the process was the origin of their former appellation by early Victorian antiquarians of "escheats". If the tenant-in-chief left a minor son as heir, that is to say one aged under 21, his wardship escheated likewise to the king, who was able to sell or award his marriage to a third party. Generally the marriages of such wards were purchased by wealthy men as husbands for their own daughters, and a marriage contract was drawn up at the direction of the bride's father which entailed the ward's future estate onto the progeny of the marriage. Thus the wealthy purchaser's grandchildren became the inheritors of the ward's estate. If the deceased tenant-in-chief left a minor daughter, that is to say one aged under 14, or one younger who was not contracted in marriage, as sole heiress (or more as joint-heiresses), her wardship and marriage likewise escheated to the king. Such wardships constituted a significant part of the royal revenues in mediaeval times.