GMS is GM employee-used to be out of stock purchase long ago. Supplier is just that. It shows up on an invoice as Supplier along with GMS. Be aware, as some are dumbfounded, GMS and Supplier portions of the discount are taxed in certain states (WI is one of them). GMS is always a better price than GM Supplier and both are not negotiable, also both are only available to a select group. Supplier is only to the person employed by the supplying company, and GMS is only to immediate family (no friends, uncles/aunts, or nieces/nephews) I am aware of GMID (?) as a GM In the Driveway-which was an has floated around as GMS under specific circumstances. The GMID is given out and signed off on by employees and executives. The last one is very rarely seen, and not by me recently. Best of luck!