For modern business travelers, it's as valuable a tool as your laptop or cell phone. It can help you win clients and close deals. You take it everywhere you go but you can't always use it. And if you use it the wrong way, it could get you fired -- or worse. What is it? It's the corporate card sitting in your wallet, and it's helping your company keep tabs on you.

The corporate card began as a way to ensure that employees could pay for what they needed -- whether last-minute airfare to Chicago or a steak dinner for 12 clients -- to win business. Corporate cards, in theory, work just like any credit card, except that the company picks up the tab. Every month the issuer would send out a statement and the executive -- or more often his assistant -- would submit his expenses.

Usually in the form of illegible and half-crumpled receipts stapled onto paper that the poor folks in the accounting department would have to decipher. As one can imagine, the opportunities for padding were considerable. Who's to know if that dinner for two was for clients or your girlfriend? And the difficulty of separating the legitimate expenses from the non was such that it was often easier to just write the check.

An Orwellian Twist

But today, thanks to new reporting software, businesses can tighten up their expenses and stop the wastage by both more closely monitoring employee spending and reducing the costs of processing the payments. It is progress with an Orwellian twist, however. Big Brother might not know what you're thinking, but he sure knows how you spend your time -- and the company's money.

Corporate cards allow companies access to detailed information on employee spending. Travel managers can now use Web-based tools to view itemized purchases...