When it comes to per diems as reimbursement for business travel expenses, including meals and incidental expenses, the employer is permitted to use any amount(s) that it wants to. If the employer uses a rate that is higher than that listed in the IRS tables, any amount above the IRS per diem rate is taxable income. If the employer chooses to use a rate lower than the IRS rate, there is no taxability to the employee.
There are a few other rules to keep in mind with regard to the high-low method. For travel within the continental U.S. in fiscal 2011, there are two levels of per diem rates that may be used in lieu of the extensive list of rates that apply to federal employees. Under this method, several high-cost localities are identified, and the applicable per diem rate for travel to one of these localities is $233 per day ($168 for lodging and $65 for M&IE). The rate for all other locations within the continental United States (CONUS) is $160 per day ($108 for lodging, $52 for M&IE). The high-low substantiation method may not be used for travel outside CONUS or if the employer’s per diem covers only M&IE.
If the employer uses the high-low substantiation method to set per diem rates for an employee, the employer generally may not switch to the per diem substantiation method for that same employee for travel within CONUS during the same calendar year. However, for travel outside the continental United States during the same year, it is permissible to switch to reimbursement for actual expenses or a meals/incidental expense per diem payment within the same calendar year, or to apply the per diem substantiation method.
Because the IRS normally revises high-low per diem substantiation rates on a fiscal year basis, employers have two options each year from Oct. 1 to Dec. 31 if they are already applying the high-low per diem substantiation method: they may continue to use the current rates and begin using the new rates from Jan. 1 to Dec. 31; or they may begin using the new rates immediately, provided those new rates are consistently applied for all employees reimbursed under this method.
Owners and relatives may not use per diem payments to substantiate travel expenses. Employees who own 10 percent of company stock and close relatives of an employer (sibling, spouse, ancestor, or descendant) must account for all travel expenses or recognize income for reimbursements and advances.