The IRS has announced the intention to discontinue authorizing the high-low method for substantiating expenses incurred for lodging, meals and incidentals while traveling away from home. Announcement 2011-42 indicates that the IRS will no longer calculate and issue authorized per diem amounts for certain high-cost localities, to be used as the high-low alternative under the accountable plan rules of Section 274(d) of the Internal Revenue Code for expenses paid or incurred while traveling away from home for business. The IRS will publish a new Revenue Procedure (Rev. Proc.) before the end of 2011, which will provide the general rules and procedures for substantiating lodging, meal and incidental expenses incurred in traveling away from home, and the high-low method will not be a part of the new Rev. Proc.
That will leave the standard federal per diem amount, or the substantiation of actual itemized costs, as methods of establishing amounts that can be paid or reimbursed for business travel lodging, meals and incidental expenses without causing the payment to be taxable income to the recipient (and also serving as substantiation that the amount is a deductible expense for the payer). After the anticipated 2011 Rev. Proc., in subsequent years no new Rev. Proc. for travel expense substantiation will be published unless the substantiation rules and procedures are changed.
The high-low method was originally created with a view to simplifying per diem payments but the IRS no longer sees a need for it. You can look up the standard federal per diem rates at http://www.gsa.gov/portal/category/21287. Or, you can reimburse for the exact amount of actual expenses, which must be documented with receipts and information on the business purpose of the expense.