Defunding the Corrupt and Incompetent United Nations Act This bill prohibits the obligation or expenditure of funds to provide contributions to the United Nations, the U.N. system, or U.N.-affiliated agencies until the President certifies to Congress that specified requirements are met, including that the U.N.: adopts a rule providing that, for its regular budget to be approved, not only must the currently required two-thirds of member states approve, but also a combination of member states whose assessed contributions make up at least 67% of the budget must approve; revises its pay structure so that salaries do not exceed equivalent U.S. civil service salaries; reinstates and conducts ongoing reviews to determine which of its mandates are outmoded and should be terminated; reinstates its Procurement Task Force; adopts reforms to make its Office of Internal Oversight Services and ethics office truly independent and strengthens whistleblower protections; and demonstrates that its peacekeepers are proactively protecting civilians and adopts changes to insure that troop contributing countries investigate and punish those found to have not followed their duties and/or to have committed crimes. Additional requirements include specified actions by the Office of Management and Budget, the Secretary-General of the U.N., international organizations receiving U.S. assistance, and the Department of State, including establishment of an office responsible for inspecting and auditing the use of U.S. contributions to international organizations. Once the President certifies that the requirements have been met, funds obligated or expended to provide assessed contributions to: (1) the U.N.'s regular budget may not exceed 18% of the total assessed contributions to such budget, and (2) the U.N.'s peacekeeping budget may not exceed 25% of the total contributions to such budget.