805. Selling the Chometz
114:1 If a Jew has chometz in his possession over Pesach, he is in continuous violation of the Biblical injunction that chometz should be neither seen nor found (Exodus 13:7, et al.). It is forbidden to have benefit from such chometz forever, even if the owner nullified it before Pesach (and even if he possessed it by accident - Mishnah Brurah 448:9). Therefore, if a person has a lot of chometz and it is impossible to get rid of it all, he must sell it to a non-Jew before Pesach, while he is still permitted to benefit from it. The selling of the chometz must not be treated as if it were academic; rather, one must intend that it is a legitimate and completely binding business transaction. He must not charge more than the going rate for the chometz. After Pesach, he should ask the non-Jew to pay the balance. If he responds that he doesn't have the money, the Jew should ask to buy back the chometz and the room. This transaction must not be treated lightly; it must be treated as a serious business transaction.
114:2 The chometz that is sold to the non-Jew must not remain in the Jew's house. It would be best if the non-Jew were to take the chometz into his house. If this is not possible, one must rent him the room that the chometz is in. One must write the buyer's name on the contract, for how much he rented him the room, and that his act of buying this property also acquires for him the chometz that is in the room (or even chometz that is elsewhere - MB 448:19). One must detail all the chometz and how much he is selling it to him for, but he need not specify the quantities; he can just write for each item the price per its measure. He should also tell the buyer verbally everything that is written in the contract. He should receive a deposit from the buyer, who will owe him the rest of the money. All this is to be written in the contract. He must also hand over the key to the room (or at the very least make it available - MB 448:12). He should not sell the non-Jew chometz together with a vessel that would require kashering because when he buys back it after Pesach, it will need to be kashered again.