Taxpayers' Conference Overspending Prevention Act or the Taxpayers' COP Act - Requires each executive agency to submit an annual report to Congress listing the amount of funds such agency obligated for conferences in the previous fiscal year, including funds for pre-planning, travel, and subsistence costs. Requires the rescission of unobligated funds for agency conferences in excess of specified amounts unless such funds are certified as being for foreign travel that is critical to the agency's mission.