Are you eligible for a discount on the iPhone 4S? Here's how to find outReady to trade in your iPhone 4 for a speedy new iPhone 4S? If so, bad news: you might end up paying a lot more than $199 for the latest iPhone, depending on the status of your contract.

The prices quoted by Apple during Tuesday’s iPhone 4S unveiling—$199 for a 16GB iPhone, $299 for the 32GB version, and $399 for the 64GB version—are for new customers or “qualifying” existing customers only.

Why? Because those $199, $299, and $399 price tags have been discounted by the carriers, who want to either a) encourage new customers to sign up or b) get long-time customers who are no longer (or almost no longer) bound by a two-year contract to sign a new one.

If you’re already under contract with, say, AT&T or Verizon and you want to get a new iPhone 4S without switching carriers, you may not be eligible for a discount—and if that’s the case for you, prepare to pay up.

Are you eligible for a discount on the iPhone 4S? Here's how to find out

Want the new iPhone, but still under contract with your carrier? Prepare to pay up.

You can check your eligibility by visiting Apple’s online store; just click the “Check eligibility” link, enter your mobile number and a few other bits of information, and you’ll learn within seconds whether you qualify for a discount. (If you’d rather not check online, you can always just call your carrier and ask.)

As for me, I bought an iPhone 4 through AT&T last June, when the then-new iPhone had just come out—meaning I’m still under contract.

I went ahead and checked my eligibility, and got the bad news: if I want an iPhone 4S before November 25, I’ll have to pay a $350 premium—or $449 for the 16GB iPhone, $549 for the 32GB version, or $649 for the 64GB model. After November 25, though, I’ll qualify for the full discount.

Verizon users with an iPhone 4 (which, don’t forget, only went on sale starting last February) may have it even worse, with Computerworld reporting that some current Verizon Wireless customers are facing an eye-popping $550 premium—think $649 for the 16GB iPhone 4S, for starters.

So, what can you do if you don’t quality for a discount?

Well, you could a) swallow hard and pay up, b) wait until you do qualify for a discount, c) switch carriers and eat the $300-ish penalty for breaking your contract (the exact amount depends on how much time is left on your service agreement), or d) call your carrier and put your powers of persuasion to the test. (Hey, it’s been known to work.)

Looking for details about the new iPhone 4S? Click here!