250 – Negative Mitzvah 250 - Not to cheat one another in business – 250 - המצווה המשלימה ר"נ - האזהרה שהזהרנו מלהונות זה את זה במסחר בשעת מקח וממכר

From Sefer Hamitzvos Daily study - Rabbi Chaim Wolosow by R Chaim Wolosow.

This mitzvah is the prohibition against wronging one another in buying and selling (ona'as mamon), from the verse "You shall not wrong one another" (Vayikra 25:14), as the Sifra explains; its laws are set out in the fourth chapter of Bava Metzia.

https://www.torahrecordings.com/rambam_sefer_hamitzvos/002/250