26 CFR § 1.162-2 - Traveling expenses.
(a) Traveling expenses include travel fares, meals and lodging, and expenses incident to travel such as expenses for sample rooms, telephone and telegraph, public stenographers, etc. Only such traveling expenses as are reasonable and necessary in the conduct of the taxpayer's business and directly attributable to it may be deducted. If the trip is undertaken for other than business purposes, the travel fares and expenses incident to travel are personal expenses and the meals and lodging are living expenses. If the trip is solely on business, the reasonable and necessary traveling expenses, including travel fares, meals and lodging, and expenses incident to travel, are business expenses. For the allowance of traveling expenses as deductions in determining adjusted gross income, see section 62(2)(B) and the regulations thereunder.
(1) If a taxpayer travels to a destination and while at such destination engages in both business and personal activities, traveling expenses to and from such destination are deductible only if the trip is related primarily to the taxpayer's trade or business. If the trip is primarily personal in nature, the traveling expenses to and from the destination are not deductible even though the taxpayer engages in business activities while at such destination. However, expenses while at the destination which are properly allocable to the taxpayer's trade or business are deductible even though the traveling expenses to and from the destination are not deductible.
(2) Whether a trip is related primarily to the taxpayer's trade or business or is primarily personal in nature depends on the facts and circumstances in each case. The amount of time during the period of the trip which is spent on personal activity compared to the amount of time spent on activities directly relating to the taxpayer's trade or business is an important factor in determining whether the trip is primarily personal. If, for example, a taxpayer spends one week while at a destination on activities which are directly related to his trade or business and subsequently spends an additional five weeks for vacation or other personal activities, the trip will be considered primarily personal in nature in the absence of a clear showing to the contrary.
(c) Where a taxpayer's wife accompanies him on a business trip, expenses attributable to her travel are not deductible unless it can be adequately shown that the wife's presence on the trip has a bona fide business purpose. The wife's performance of some incidental service does not cause her expenses to qualify as deductible business expenses. The same rules apply to any other members of the taxpayer's family who accompany him on such a trip.
(d) Expenses paid or incurred by a taxpayer in attending a convention or other meeting may constitute an ordinary and necessary business expense under section 162 depending upon the facts and circumstances of each case. No distinction will be made between self-employed persons and employees. The fact that an employee uses vacation or leave time or that his attendance at the convention is voluntary will not necessarily prohibit the allowance of the deduction. The allowance of deductions for such expenses will depend upon whether there is a sufficient relationship between the taxpayer's trade of business and his attendance at the convention or other meeting so that he is benefiting or advancing the interests of his trade or business by such attendance. If the convention is for political, social or other purposes unrelated to the taxpayer's trade or business, the expenses are not deductible.
(e) Commuters' fares are not considered as business expenses and are not deductible.