The physical search for leaven is only half the practical solution Jewish law developed for the problem Passover creates, since a household cannot always destroy or consume every trace of leaven it owns before the festival, particularly bulk goods such as whisky, flour or pet food that would be wasteful or expensive to discard entirely. The parallel mechanism, mechirat chametz, the formal sale of chametz, allows a person to sell their leaven, on paper, to a non-Jewish buyer for the duration of the festival, transferring legal ownership so that the prohibition against a Jew owning leaven during Passover is satisfied without the goods being physically destroyed, and the sale is reversed automatically once the festival ends, restoring ownership to the original party.
In contemporary practice this sale is almost never conducted personally between individuals; instead a rabbi acts as an agent, authorised by a written power of attorney signed by congregants, who bundles the community's collective chametz into a single sale to one buyer, a document and transaction now handled routinely by synagogues each year and, increasingly, through online forms that let a household authorise the rabbi's sale on their behalf without an in-person meeting. The relationship between the two practices, the search and the sale, shows the same layered structure common elsewhere in Jewish law: bedikat chametz enacts a search and a spoken nullification that Torah law technically requires nothing more than, while the sale mechanism handles the much larger practical volume of leaven a modern household or business actually owns, a division of labour between a symbolic domestic ritual and a formal legal instrument operating on an entirely different scale.