When you travel for work, you know the drill: Get receipts for everything. When you spend cash for stuff like meals, beverages, hotels, and rental cars, your employer is likely to pick up the tab as long as you've got proof of purchase.

But what if you have to spend money on the road but can't get a receipt? It's happening more and more. The major airlines have deployed their newest fees with such haste that they are not always equipped to issue receipts for on-board purchases. Ask a flight attendant for one, and on some carriers you're more likely to receive a blank stare than appropriate documentation.

Take U.S. Airways. As of Aug. 1, the carrier began charging for drinks of any sort, including $2 for water. Passengers are not permitted to carry their own beverages through security, and buying drinks in the terminal is not always possible either because of a time crunch or because of personal dignity over gouging. If you, a business traveler, decide during Hour Three of a flight that you're thirsty, the staff will sell you a drink but they won't be able to give you a receipt.

I called U.S. Airways to ask if any of its flight attendants were equipped to furnish receipts for this newfangled charge. The answer was no. Right now, an airline rep told me, there are "plans" to give on-board staff hand-held devices for printing receipts by the first quarter of 2009, but for now, they have nothing, and those nebulous "plans" could not be elucidated for me. U.S. Airways' flight attendants also have neither the training or the equipment to write receipts by hand.Not long ago on American Airlines, I requested a receipt for a gin and tonic I ordered during a long trip. The flight attendant told me he couldn't do one. And what's more, he told me, I shouldn't get one because no company pays expenses on alcoholic drinks. (They do when you're a travel writer reviewing an airline's service, I thought, but I said nothing.) Eventually, when I said that I would like one anyway, he vanished for about a half an hour and came back with some improvised scratch on a fragment of cardboard. It did the trick and I got my money back. But it clearly annoyed the guy and disrupted his day, and I was made to feel as if I did something wrong by asking.

A lack of receipts and on-board bookkeeping could even open the door to theft among flight crew, but that's the airlines' problem. I'm more concerned about business travelers who, unless they have a particularly forgiving and trusting accounting department, will have to swallow some of these new costs. That is, until the airlines follow the usual rules of civilization and issue receipts.

The burden is shifting toward the business traveler even on airlines that get receipts right. Meals were once included in the ticket price, so employers paid for them when they bought the seat. Now that food is usually charged separately, meals (and anything not included in the ticket price, like American Airlines' $15 bag-check fee), must come out of employees' pockets. More airlines are going cashless, such as Frontier, Virgin America, AirTran, and JetBlue. (U.S. Airways, ever the backward renegade, is still cash-only.) So for many carriers, you will at least be able to put charges on a credit card so that your bean-counters can clearly see an itemized list.

The charge appears on your bill, but getting that money back from your company can still take a while. It's not unusual for employees to be left holding the bag for several months, bearing interest charges on their accounts while their employer gets around to reimbursing them.

Employees are being asked, in effect, to float their employers with mini-loans from their own personal funds. That's a trend that has more to do with business economics than travel fees, but it compounds the problem. Still, the more business travelers have to pay a personal price for these charges, the more they will blame the airlines for the inconvenience.