Know your tax rules. If you are on same-day travel for more than 12 hours, you can get reimbursed for meals and incidental expenses but the reimbursement is considered taxable income. If you do deal with hotels directly about their prices, make sure they include taxes in the rate they quote. Often hotels will set room rates at per diem and add taxes on top of that, Tirrell says. Don't confuse business with pleasure.
Travelers run into trouble in two areas here.
First, if you are flying for business and want to take a different route for personal reasons, you can do that. But the government will only pay for the part of the trip that is business related. And you won't get the government contract fare on your personal trip you have to pay the standard commercial fare. But you won't if you leave a long-term TDY location for personal travel. Submit early and often.