The Quarterly Security Count Rule (Rule 17a-13). This SEC rule requires a broker-dealer on a quarterly basis to count, examine, and verify the securities it actually holds for customers and for itself — and compare that with the amounts of such securities it should be holding as indicated by its records. This process includes verifying the actual amount of securities located at sub-custodians such as the Depository Trust and Clearing Corporation, or DTCC. If there are differences between the actual amounts held and the amounts that should be held, the broker-dealer must take capital charges until the differences are resolved.