When can I deduct part of my vacation as a business expense?

You can deduct travel costs only if the "primary purpose" of the trip is business, not personal. That means more than half the time you are away from home must be spent on business activities.

Simply visiting another provider or attending a training for one or two days during a seven day vacation does not make this a business trip. If you do spend one of seven days on business activities, you could deduct one night in the hotel and the mileage to the business locations and one day of food expenses. But that's it.