3 Rental Car Bill Hazards

Nearly all business travelers have experienced last-minute surprises when their final car-rental bills far exceed what was quoted. Here's what to look out for:

• Local taxes/fees: When shopping for car rental rates, be sure you're comparing apples to apples--meaning all taxes and fees should be part of every rate quote. Always ask. Taxes and fees (often used to fund construction of convention centers or stadiums) can increase your final bill by up to 71 percent, according to a Travelocity.comstudy, which ranked airports where rental car fees are steepest.

• At Houston's Intercontinental Airport, for example, if you rent a car for two days at $50 per day, you'd expect your bill to be about $100. But with taxes and fees, you'll end up paying a whopping $171. Other airports that ranked high on Travelocity.com's list include Austin, Cleveland, Dallas/Fort Worth and Houston-Hobby.

• Frequent fliers: Most rental car companies now add a surcharge to those customers earning airline frequent flier miles for their rentals. Expect to pay 50 cents per day, up to a maximum of $2 per rental, for the honor of earning those miles.
• Insurance: This is one car-rental fee you can do something about. When it comes to collision or liability damage waivers, don't fall for rental car agents' hard sell (they earn a commission selling these add-ons, which can cost as much as $30 a day). Typically, if you own a car and have insurance, you're covered when driving a rental car. In addition, many major credit cards offer insurance if you charge the rental car on the card. Before your next trip, call your insurance company or credit card company and ask whether you're covered.