An audit of the District’s computerized tax processing system found weaknesses, inefficiencies and a lack of internal controls that have cost the city at the very least tens of thousands of dollars — and probably much more.

D.C. Auditor Deborah Nichols’ review of the Integrated Tax System, sought by the D.C. Council, found the Office of Tax and Revenue was slow to deposit tax payments and often paid too much interest on delinquent refunds, resulting in losses of thousands of dollars at a time.