You are traveling away from home if your duties require you to be away from the general area of your tax home for a period substantially longer than an ordinary day's work, and you need to get sleep or rest to meet the demands of your work while away.
You can start thinking travel deductions when you have to leave your tax home for more than one day, and probably have to sleep in a hotel somewhere and buy yourself something to eat at least.
Keep in mind that the IRS will only allow you to deduct temporary travel assignments (less than one year). Whereas, travel assignments that are indefinite (over one year) are NOT deductible.
Wait. What's a "tax home?" Glad you asked.
Your tax home is generally the city and surrounding suburbs where you work and conduct business. However, it is more and more common for people to work during the week in one place, and then fly/travel home on the weekends. So where is a tax home in these cases?
Let's say you work Monday - Friday in Seattle, but your family lives in Spokane where you fly home every weekend to be with them. Can you write off the expenses incurred traveling to and from Seattle? Can you write off your Seattle hotel expenses or apartment rent in the city? NOPE.
Why? Because Seattle is your tax home: it's where you do business. It's also an "indefinite" work assignment. You'll be working there until...you're no longer working there.
What if you worked and lived in Spokane, and you had to fly to Seattle for 6 days for a convention that related to your business? Can you write off those expenses? Absolutely. Why? It's a temporary assignment, and you'll be there for more than one day.
Going to San Diego for a convention? Want to bring your spouse and maybe your kids along so they can spend some time on the beach--and maybe you can join them there? Sure. Go ahead, but here's what you need to be aware of:
It is quite common for people to spend an extra day or two in a new place to see the sites and maybe wind down from a busy week selling, networking and workshopping. If it's your first time traveling to New York City or Chicago it would be difficult to just hop back on a plane without seeing museums, plays, or eating all that food you've heard so much about, right? Go ahead and take some time to enjoy yourself, but you'll want to keep these things in mind:
Speaking of keeping records...
Still confused about what you can write off for business travel expenses?
What to Read Next:
Home Office: Personal vs. Business Expenses
Are You Fudging Your Personal vs. Business Expenses?