If a former self employed consultant in my business has left and approached and agreed terms with an existing client of mine, is that considered stealing in Jewish law?
Jewish law discusses the matter of “poaching” clients, which is known as maarofia.
The Rashba (3:83; 6:259) writes that if a Jew has a regular client, it is not permitted to “poach” the client away, because the Jew is relies on the custom of his regular client (the idea is derived from the Gemara in Bava Basra concerning somebody who has already laid out a net to catch fish). This is considered “stealing” a person’s income.
This idea is ruled by the Rema (156:5).
However, the practical ruling will depend on the circumstances of each case. For instance, if the consultant is the person who brought in the clients, and they were actually “his” clients more than the company’s, then the halachah will not apply.