Debts in the Store - Shemitat Kesafim and Prozbul

I sell ice cream from a truck on Fridays, and people owe me money for what they bought. Do I also need to make a Prozbul, or is it only for those who actually lent money, and not for those who gave ice cream on credit?

If the purchase in the store was on credit, the debt is not canceled. However, some say it is considered like a loan, and the debt is canceled. Therefore, it is advisable to make a Prozbul so that according to all opinions, you can collect the debts.

In the Mishnah of Shevi'it (Chapter 10, Mishnah 1), it is stated that the Sabbatical year cancels loans, whether documented or not. "Store credit" is not canceled, but if it is made into a loan, it is canceled. "Wages" are not canceled, but if made into a loan, they are canceled. Two approaches explain why "store credit" and "wages" are not canceled. The first approach - [the opinion of most early authorities, see Tosafot, Gittin 18a, s.v. Me'eimatai, Tosafot, Ketubot 55a, s.v. Ve-leshevi'it, and early authorities in Ketubot there, see Ramban and Ritva there, and Meiri, Gittin 37] that only a loan is canceled, but a debt incurred through sale or wages, or any other way - is not canceled. The second approach - Rambam's opinion as explained by Beit Yosef (Choshen Mishpat, Siman 67) and Kesef Mishneh (Chapter 9, Laws of Shemitah and Yovel, Halacha 11), and this is also the law in Sema (Siman 67, S.K. 26) and Shulchan Aruch HaRav (Laws of Loans, Paragraph 39), that not only a debt created by a loan is canceled, but any debt is canceled, even if created by sale or work or any other way, but the reason "store credit" and "wages" are not canceled is because in their time it was customary to buy in the store on credit for a long period, and only when a very large amount accumulated, then they would pay, and if at the end of the Sabbatical year the debt is not yet due for collection, it is not canceled, and similarly for "wages", it was customary not to pay immediately but only after a large amount accumulated, and at the end of the Sabbatical year the debt is not yet due for collection. There is a practical difference between the two approaches, in our time, when it is usually customary to pay after a short time, such as a monthly salary paid to a worker, according to most early authorities, it is not canceled, because it is not a debt due to a "loan", but according to Rambam, it is canceled. Also, "store credit" in our time, when it is customary to pay once a month, according to most early authorities, is not canceled (if not made into a loan) because it is included in the category of "store credit", but according to Rambam, it is canceled because "store credit" mentioned in the Mishnah is only in a case where at the end of the Sabbatical year the debt is not yet due for collection. However, even in the case of "store credit", if it was "made into a loan", the debt is canceled [and this is the intention of the aforementioned Mishnah "if made into a loan, it is canceled"]. What is "made into a loan", there are many opinions, and we will detail some of them: the opinion of the Rosh (Tractate Gittin, Chapter 7, Siman 17), that it is setting a time for repayment of the debt before Rosh Hashanah, and the opinion of Mordechai (Tractate Shevuot, page 8 according to Mordechai), if the summary of all the debt was written together. (Azmera Le-shimcha, Laws of Shemitah).