It used to be that if your landlord gave you a preferential rent, you could automatically count on future increases being based on that rate. In 2003, policy adjustments at the Division of Housing and Community Renewal (DHCR) changed that. Now, unless the preferential rent is for your whole "tenancy," which includes the period beyond the initial lease term, at renewal the landlord is allowed to raise the rent to the full legal rate. This means the rate it would have been, if you hadn't been offered the preferential rent to begin with. However, subsequent cases have interpreted these amendments to bar landlords from doing this, when tenants can prove that the intention was for their preferential rate to last for the entire tenancy. Usually, both sides argue about the lease's wording and the parties' intentions, ending up in court. In the future, if your initial lease includes a preferential rate, make sure it has specific language that validates its application to all future renewals.