A person's travel expenses can become a legal matter for various reasons. For example, the U.S. government reimburses witness for the cost of traveling to and from the courthouse under 28 U.S.C. 1821. And taxpayers can claim tax deductions for certain business travel expenses under 26 U.S.C. 162.
Per Diem and Mileage Rates: Under certain laws, a person's meal, lodging and incidental travel expenses are figured using a flat rate for each day of travel, known as a Per Diem rate. Similarly, a person's transportation expenses may be figured using flat rate for each mile of travel, known as a Mileage Rate.
Some Federal and state laws specify the applicable Per Diem or Mileage rate. These figures are found in the United States Code or the relevant state statutes.
Others laws use Per Diem and Mileage rates set by Federal agencies. Most of these rates are posted on the Internet, including:
The CONUS Per Diem rates set by the General Services Administration for travel in the contiguous 48 states (http://www.gsa.gov/Portal/gsa/ep/channelView.do?pageTypeId=8203&channelId=-15943);
The OCONUS Per Diem rates set by the Department of Defense for travel in Alaska, Hawaii, Puerto Rico, the Northern Mariana Islands and U.S. possessions and territories (http://perdiem.hqda.pentagon.mil/perdiem/perdiemrates.html);
The Foreign Per Diem rates set by the State Department for travel abroad (http://aoprals.state.gov/content.asp?content_id=184&menu_id=78); and
The Privately Owned Vehicles POV Mileage Reimbursement Rate set by the General Services Administration for travel by automobile, motorcycle or airplane.
Because these rates are relevant for tax purposes, these rates are also reported in tax news sources, such as Tax Notes Today, and the large tax looseleaf services, such as CCH's Standard Federal Tax Reporter. The Privately Owned Vehicles Mileage Reimbursement Rate is also published in the Federal Register.