The procedure used today for mechirat chametz developed in various stages. Originally, the sale of chametz was like any other sale, as described above. Later, it became common to include an unwritten agreement that the non-Jewish buyer would sell the chametz back after Pesach. Over time, as more Jews found themselves with considerable quantities of chametz on erev Pesach, it became impractical to physically transfer the chametz, and non-Jewish buyers became reluctant to lay out such large sums of money. One reason for this development was that Jews in medieval Europe were not permitted to own land. Thus, some got involved in selling beer. Had they been required to destroy their entire stock before Pesach, their businesses would have been ruined. At this point, rabbis began arranging sales for individual merchants. The sales were formal, but the chametz would remain in the Jewish-owned warehouses and the non-Jewish buyers would pay a fraction of the authentic value, leaving the remainder as a loan; after Pesach, the Jewish business owners would buy their merchandise back.
This method presented a new problem: how to deal with chametz that remained in the Jewish owner’s home or property. In the original method, the buyer removed the chametz from the Jewish individual’s house (Terumat Hadeshen 120) so that it should not appear that he has responsibility for it (MA, OC 448:4). Moreover, this way he would not come to accidentally eat it (Shu”t Radbaz 1:240). The Bach (OC 448:2) approved selling one’s stock of beer in conjunction with an innovation—together with the beer, the storeroom had to be sold or leased to the non-Jewish buyer. This phase lasted from about the early seventeenth century to the early nineteenth century when the final innovation was introduced.
The final stage in the development of mechirat chametz is more or less what exists today: a rabbi arranges a general sale of the chametz for the members of his community. In this sale, the non-Jew does not take possession, does not pay the full value of the chametz and he sells it back after Pesach. This mass sale is only about 200 years old and was originally opposed by many authorities who viewed it as blatant ha’arama. It has since been widely accepted and is normative practice today. Rabbinic authorities continue to modify various aspects, ensuring that the transaction is a legal and fully binding sale, and not a mere formality. It has become so accepted that the Mishnah Berurah (433:23) even suggests selling certain areas in one’s home that may be too difficult to check for chametz.
Ari Z. Zivotofsky, “What’s the Truth about . . . the Sale of Chametz on Pesach?, Jewish Action (Spring 2015), 98-99.