Point of Service Plan (POS) — a health maintenance organization (HMO) or preferred provider organization's (PPO's) program that allows members to seek treatment from providers outside the network (that is, providers not employed by or under contract with the organization) at a reduced benefit level, commonly 60 percent or 70 percent of in-plan coverage, or at a higher premium. There is usually an additional fee for using the POS (out-of-network) option. Also known as open-ended plan.