You probably know that if you promptly refund an overcharge to a tenant who has filed a rent overcharge complaint against you, the Division of Housing and Community Renewal (DHCR) shouldn’t hit you with triple damages for the amount of the overcharge. But to avoid that penalty, your refund must also include interest (currently set at 9 percent per year) on the overcharge amount, warns Steven Sidrane, of counsel to the Hewlett, N.Y., law firm of Sidrane & Schwartz-Sidrane, LLP.