(MONEY Magazine) - Consider, just for a moment, the swirl of the modern health-care system. One wrong keystroke by a hospital administrator can land you in red tape hell. That's enraging--and scary. "Would you believe a thousand-dollar toothbrush?" says Nora Johnson, a medical-billing auditor who has seen that and a lot of other absurdities. "More than 90% of the bills I review are either wrong or padded beyond belief." Her own husband was once charged for blood tests for a newborn as part of his hip-replacement surgery. ("I was pretty sure he hadn't had a baby.") If billing errors result in overcharging or, worse, a denied claim, understanding the bureaucracy--the very thing that drives you nuts--is your best offense.

How to Fight Back

1 KNOW THE CODES Your bill will be awash with medical shorthand for the treatment you received. There are two kinds of codes:

• Diagnostic codes (a.k.a. ICD-9 codes), which identify what was wrong with you

• Procedure codes (a.k.a. CPT codes), which describe what treatment you received

Coding problems can be the result of either blatant padding (one procedure to remove tonsils and adenoids is "unbundled" and billed as two separate procedures) or keystroke errors (one typo causes a mismatch between the ICD-9 and the CPT codes, and your claim is branded a "coding error" and rejected). If your claim bounces back or the bill seems high, ask the hospital or doctor for a thorough explanation of each and every code.

2 BE MORE PREPARED THAN THEY ARE KO PUNCH Everyone knows you're supposed to hang on to bills, but here's something most people miss: doctor's orders. Every time your physician prescribes something--blood tests, X-rays, medication--it's recorded in her standing orders. You have a right to this stuff, so request a copy from the billing office. Keep it in a personal medical file, which should also include the following documents:

• Reports by any technician handling a procedure, as well as the nurses who administer medication or shuttle you around in your paper gown

• Itemized bills (request these from your doctors or hospital, possibly after your treatment visit)

• Your insurance paperwork

• Your own notes from each doctor visit

3 DEMAND RELIEF BY CERTIFIED MAIL Send (certified) a detailed letter to your doctor's office or hospital requesting a corrected bill. Then send (certified) another, equally detailed letter describing the problem, including your documentation, to the insurer. Don't forget copies of the doctor's orders and the bill.

If the doctor did order a test or procedure but the orders weren't carried out, you'll need documentation proving that. (Paperwork, as you may have surmised, is pretty much your lifeblood here.) Most insurers have a time limit, typically 30 or 60 days, within which they'll consider routine appeals. So get a move on.

OTHER STUFF YOU HATE

The Problem

Useless Miles

Tim Winship, editor of FrequentFlier.com, says it's getting harder to turn

miles into a seat on a plane going your way. Airlines may dangle an

"unrestricted award," which gets you a ticket with fewer restrictions

but costs twice as many miles. This is more expensive than it looks: Miles are

usually worth about a penny each, so using even an extra 25,000 would run you

$250.

How to Fight Back

Switch in Cleveland

Winship recommends asking the airline to create an alternative

itinerary--perhaps making an extra connection through a less-busy airport--that

lets you use your miles. (Most airline websites aren't sophisticated enough for

you to do this yourself, he says.) Many airlines charge $10 to book through a

real person, but that's a bargain compared with giving up twice as many miles.

And they might even waive the fee if you ask nicely.

30% of medical bills contain a coding error.

SOURCE: National Fee Analyzer.

Watch out for double billing. It's common when you've

been admitted through the E.R. or you've seen a bunch of doctors.