As of January 26, 2010, U.S. Customs and Border Protection (CBP) will require that all importers comply with the Importer Security Filing (ISF), also popularly known as "10 +2" because of the 10 elements required to be provided to CBP relevant to the importer and 2 elements required to be provided to CBP relevant to the carrier. CBP has announced that as of January 26, 2010, it will also begin to issue penalties of either $5,000 or $10,000 against importers who fail to comply with ISF; something CBP calls its "enforcement phase". Importers who self-file ISF, or their agents, must understand the changes, comply with them, and, when a penalty is issued by CBP, respond in writing to mitigate the penalty.