When people talk about identity theft, they usually mean one thing: someone getting your name, birthday, and social security number. With this information, they then apply for credit in your name. They keep the money, and you’re stuck with the bill (and the bad credit).

That’s the fastest way for identity thieves to make a quick buck, and your credit monitoring is your first line of defense. With credit monitoring, you’ll get an alert every time someone applies for credit in your name.

But there are other kinds of identity theft that don’t show up anywhere on your credit report and can be just as damaging. Here’s what you need to know:

Employment Identity Theft

To get a job in the United States, you need to have a social security number. If you’re a citizen or have a legal work visa, you’ve got an SSN. But illegal aliens don’t have social security numbers, and therefore have to either find someone willing to pay them cash under the table (which is most common), or they have to find an SSN they can steal.

There’s a whole underground black market for illegal aliens to steal people’s identities. Criminals will sell them a name and an SSN, and then they give that info to their employers. Their employers think they’re legally allowed to work, and report payroll taxes just like they would for their other employees. If you’re the real owner of that name and SSN, guess what? The IRS now thinks you’re making more money than you say you are. This can be an absolute nightmare. And your credit report may never catch it. You might not find out it has happened until months or years later when you get a letter from the IRS. Which brings us to the next kind of ID theft:

Tax Return Identity Theft

If someone can get a hold of your personal information, they can file a false tax return in your name and pocket the refund. This kind of scheme is a more difficult to pull off (think of all the documents you’d need!), but it does happen.

Again, this will not show up on your credit report, even after it has happened. Your best defense here is to guard your information as well as you can, and file your tax return early.

Medical Identity Theft

If someone gets your health insurance information, they can walk into a doctor’s office pretending to be you, get medical treatment, and stick you with the bill. Actually, it’s the insurance company who pays out most of the money, but that still affects your deductible, etc.

Even more frightening is the prospect of having the identity thief’s medical history confused with yours.

Watch your health insurance claims carefully. You can view pending and approved claims online, so do this vigilantly and notify your insurer if they have processed any claims that aren’t actually yours.