EOB vs. medical bill: how to read both

The five numbers on an EOB

Every EOB, whatever the layout, reduces to the same five figures.

• Billed / charged — the provider's list price. Almost never what anyone pays.
• Allowed amount — the contracted rate your plan and provider agreed on.
• Plan paid — what the insurer sent to the provider.
• Adjustment / write-off — the difference between billed and allowed, which an in-network provider must eat.
• Patient responsibility — deductible + coinsurance + copay. This is your number.

Matching the EOB to the bill

Take the patient-responsibility figure from the EOB and compare it to the balance on the provider statement for that same date of service. They should match.

If the provider is in-network and is billing you more than patient responsibility, they may be billing you for the write-off amount, which their contract usually prohibits.

Denial and adjustment codes

The small codes on your EOB (CO-45, PR-96, CO-197 and friends) tell you why a charge was reduced or denied. 'CO' means the provider is contractually obligated to absorb it. 'PR' means patient responsibility. That prefix alone often settles who owes what.

When the two disagree

Call the provider's billing office first with the EOB in hand — many discrepancies are timing artifacts where the provider billed before the insurer finished processing. If the balance is still wrong after the EOB posts, that is when you send a written dispute.