Coordinated Issue Papers (CIPs) provide guidance on technical tax questions, such as medical reimbursement plans for the self-employed, that is reviewed by the Office of Chief Counsel and provided to revenue agents.
CIPs are numbered using the Uniform Issues List (UIL), an index of issues based on Internal Revenue Code Sections. For example, a CIP about medical reimbursement plans for the self-employed was issued in March 1999 under UIL number 162.35-02.
CIPs are reflective of IRS thinking, but are not authoritative.
A list of CIPs can be found online at the IRS web site.