The MTCN is usually 10 digits long and is required to be written on the retrieval paper alongside with the receiver's and sender's name, address, postcode, country. MTCN is an acronym, that stands for Money Tranfer Control Number (not to be confused with the other MTCN: Minimum Throughput Class Negotiation). It is a number that is given to you after you have transferred any amount of money through the service of Western Union. The number then can be used by the supposed receiver to retrieve the money that the sender had sent. The MTCN is very IMPORTANT so please keep the receipt until the receiver has retrieved the money.