That Letter You Tossed? It May Have Contained a Billing Error Worth Fighting

Every few weeks, a plain envelope arrives from your health plan or Medicare Administrative Contractor. Inside is an Explanation of Benefits — an EOB — and for most Americans, its destination is the recycling bin.

That is a costly habit. Fraud investigators and billing auditors consistently find that a meaningful share of improper payments are visible on the face of the EOB, if only someone reads it. For seniors on Medicare Advantage and supplemental plans, whose claims volume is highest and whose tolerance for billing disputes is often lowest, the stakes are especially real. Here is what to look for.

Red Flag 1: A Service You Do Not Remember

The EOB lists every service a provider billed — including services that were never performed. A physical therapy session on a date you were out of state. An office visit the day before your procedure when you never came in.

Action step: Keep a simple calendar of appointments. When the EOB and your calendar disagree, call the provider's billing office and request the documentation supporting the charge. If the answer is evasive, report it to the HHS Office of Inspector General hotline — billing for services not rendered is federal fraud, not a billing dispute.

Red Flag 2: The Same Code, Twice

Duplicate billing is the most common error in claims processing. A test performed once appears under two dates, or a surgeon bills the same procedure under both a hospital claim and a personal claim.

Action step: Scan for identical CPT codes with identical dates. If you find one, request a corrected claim in writing. Do not pay either instance until the duplicate is resolved.

Red Flag 3: Upcoded Visits

Evaluation codes run on a complexity scale. A brief follow-up should bill as a low-level visit; if your ten-minute blood pressure check is billed as an extended, high-complexity consultation, your cost-sharing rises with it.

Action step: Ask the office what level of visit was billed and why. For Medicare beneficiaries, request the visit documentation; you are entitled to your own records under HIPAA.

Red Flag 4: 'In-Network Savings' That Do Not Add Up

EOBs show a discounted rate negotiated with in-network providers. Occasionally the arithmetic is wrong — the discount is applied, then the patient responsibility is calculated on the undiscounted charge anyway.

Action step: Recalculate with a calculator, not trust. If your share is computed on the pre-discount amount, dispute it in writing and cite the line item by claim number.

Red Flag 5: Balance Billing After an In-Network Visit

If a provider is in-network, the line marked "patient responsibility" should match your plan's cost-sharing — nothing more. A separate charge from the provider for the "remaining balance" is illegal in many contexts and restricted in most.

Action step: Forward the provider's collection letter to your plan and your state insurance department. Under the No Surprises Act, many balance-billing scenarios carry federal protections.

Red Flag 6: Services Billed Under Someone Else's Identity

Medical identity theft often surfaces first on an EOB: a colonoscopy you never had, a durable wheelchair you never received. Seniors are frequent targets precisely because claims volume makes anomalies hard to spot.

Action step: Request your annual Medicare Summary Notice review, and pull your medical records for the period in question. Then file a report with the Federal Trade Commission and notify your plan's fraud unit.

Red Flag 7: A Denial Buried in Fine Print

Not every EOB problem is overbilling. Some are under-advocacy: a covered service denied for a technical reason — a missing referral, a coding mismatch — that the provider's office could fix in one phone call, but never will unless you ask.

Action step: Every denial notice includes an appeal deadline. Mark it on your calendar the day the EOB arrives. Medicare Advantage appeals follow strict timelines, and missing them forfeits rights you can never recover.

A Five-Minute Habit Worth Thousands

Reading an EOB is not paranoia; it is the only audit system most American patients will ever personally control. Keep the letters in one folder, check them against your calendar, and act within 30 days when something looks wrong. The errors are real, the corrections are obtainable, and the first person positioned to catch them is the one holding the envelope.