Am I due commission payments after I leave a company?

There is no general answer: unlike salary and wages, commissions are governed mostly by the agreement between employee and employer as to the terms for commissions (rather than by fixed or set laws). It would be legal to pay employees for all commissions earned, even after they leave employment; it would also be legal to not pay employees any commissions, even if previously earned, once employment terminates. It depends on what the agreement or arrangement was. If you were to sue for the money, the court would try to determine the shape of that agreement or arrangement. It would first look to any employment or commission contract/agreement; if there was none, to any handbook, memos, correspondence, emails, etc. which explicated the arrangement; if nothing at all in writing, it would look to past practice--what happened to other commissioned employees when their employment ended? Where they paid? And if there is no past precedent or practice (new company, or you are the first commissioned employee to leave it), a court would look to industry practice in your area--what do like companies do? Whatever is found to best represent the agreement or arrangement under which you worked would typically determine if you were due commissions or not.