In general, there are three types of IRS written determinations: Taxpayer-specific rulings or determinations are written memoranda furnished by the IRS National Office in response to requests by taxpayers under published annual guidelines. See Rev. Proc. 2008-1 and Rev.Proc. 2008-4 for more information about these guidelines. Technical advice memoranda (TAM) are written memoranda furnished by the National Office of the IRS upon request of a district director or chief appeals officer pursuant to annual review procedures. See Rev. Proc. 2008-2 for more information about these procedures. Chief Counsel Advice (CCA) materials are written advice or instructions prepared by the Office of Chief Counsel and issued to field or service center employees of the IRS or Office of Chief Counsel. See the Chief Counsel Advice Training Materials for more information about CCAs.