The Competent Authorities of Canada and the United States have signed a memorandum of understanding (MOU) setting out the principles, guidelines and procedures to be followed in resolving factual disagreements in mutual agreement cases under the 1980 US-Canada income tax treaty. The MOU was signed on 23 December 2005 and follows the MOU signed on 3 June 2005 that formalized the mutual agreement procedure (MAP) for resolving cases of double taxation under the treaty. It also follows the announcement by the US Internal Revenue Service (IRS) and the Canada Revenue Agency (CRA) on 8 December 2005 that they had reached agreement on procedures for resolving factual disputes in the MAP process.