The rules apply for travel outside the 50 states and the District of Columbia. Travel to the possessions is considered travel outside the U.S. Travel outside the U.S. does not include any travel from one point in the U.S. to another point in the United States, even though part of the trip is outside the United States.

Allocation is done on a day-to-day basis, in proportion to the number of nonbusiness days during the trip to the entire trip. Each day is considered either entirely a business day or entirely a nonbusiness day. A day spent outside the U.S. is deemed a business day, even though only part of the day was spent on business, if any of the following apply:

• The taxpayer was traveling to or returning from a destination outside the U.S. in pursuit of a trade or business.
• The taxpayer's presence outside the U.S. on that day was required at a particular place for a specific business purpose.
• During hours that are normally considered appropriate for business activity the taxpayer's principal activity was the pursuit of a trade or business.

If the trip is primarily personal in nature, travel expenses to and from the destination are not deductible, even if the taxpayer engages in business activities while at the destination.

Once the amount of travel expenses subject to the allocation and disallowance rules is determined, that amount is multiplied by a fraction, equal to the number of nonbusiness days during the trip, divided by the total number of business and nonbusiness days during the trip.

These restrictions do not apply when any of the following conditions applies:

• Travel time outside the United States do not exceed one week.
• Nonbusiness travel time is less than 25 percent of the total time.
• The individual lacks substantial control over the travel arrangements (other than the timing of the trip).
• The vacation portion of the trip is a not a major consideration of the taxpayer.