Insurance paid less than the estimate. What to do.

The estimate said $800. The insurer paid $450. Before you send the patient a bill for the difference, find out whose mistake it is. Often it's a real patient balance. Sometimes the insurer owes you, and nobody asks.

Step 1: read the codes on the EOB

Every reduction on the explanation of benefits (EOB) or electronic remittance has a code. The two letters in front decide who pays: PR means the patient may owe it, CO means the office can't bill the patient for it. Look each one up in our denial code library.

Step 2: find which of these happened

Reason	What happened	Who usually owes it
Deductible applied	The patient hadn't met the plan-year deductible, or the insurer applied it to a service the plan normally exempts (often preventive).	Patient, unless the deductible was already met or shouldn't apply
Annual maximum used up	The plan paid up to its yearly maximum. Look for code 119 on the EOB.	Patient, if the remaining maximum on record is right
Frequency limit	The plan allows the service only so often (for example cleanings, bitewings or perio maintenance), and the insurer counted an earlier one, sometimes from another office.	Patient if the date is right; insurer if the earlier service date is wrong
Alternate benefit (downgrade)	The plan paid for a cheaper procedure, such as an amalgam rate for a posterior composite, or a different code than billed.	Patient for the difference if the plan has that clause; insurer if your contract or the plan doesn't allow it
Missing tooth clause	The plan won't pay to replace a tooth lost before coverage started (common for bridges and implants).	Patient, if the extraction date really is before coverage
Waiting period	Major or basic services aren't covered until the patient has been on the plan long enough.	Patient, if the waiting period still applied on the date of service
Coordination of benefits	The insurer thinks another plan is primary (code 22), or reduced its payment for what the primary paid (code 23).	Usually the other insurer: bill the primary first
Wrong percentage or fee	The insurer used the wrong benefit class (basic paid as major) or an allowed amount below your contracted fee.	Insurer: ask for reprocessing
Bundling	The insurer folded one procedure into another done the same day (code 97).	Usually a PPO write-off; appeal only if the services were separate

Step 3: check the allowed amount against your contract

This is the one most offices skip. Find the allowed amount on the EOB and compare it with the fee your PPO contract lists for that procedure code. If the allowed amount is lower, the insurer underpaid you. The patient doesn't owe it, and you shouldn't write it off.

Also check the code the insurer paid. If you billed one code and the EOB shows a cheaper one, that's a downcode. It may be an alternate-benefit clause (patient's share) or a processing error (insurer's).

Step 4: if the insurer is wrong, ask for reprocessing

Call provider services with the claim number and ask for reprocessing. Write down the call reference number.
If they won't fix it on the phone, send a written reconsideration request with the evidence: the fee schedule page, the eligibility printout, or the prior service dates.
Set a follow-up date. Most reprocessing requests that go quiet were never worked.

Step 5: if it's a real patient balance, explain it

Send the bill with the EOB and a one-line reason in plain words (“your plan's yearly maximum was reached in June”). Patients pay faster when they understand why the estimate changed.

Prevent it next time

Check remaining maximum, deductible, frequency history and waiting periods before major treatment.
Ask about other coverage at every visit.
Keep each PPO fee schedule on file and compare every payment with it, not just the ones that look low.
Send a pre-treatment estimate for large cases and give the patient a written range, not a single number.

Want to know how often this happens to you? Add your insurer payment files and PPO fees to the free check. It compares every payment with your contract and flags underpayments and downcodes. It runs in your browser; nothing is uploaded.

Run the free check

General information for dental billing staff, not legal advice. Plan terms and insurer rules vary; check the patient's plan and your contract.