Most practices track denials closely. Far fewer track underpayments, even though they can cost as much, because nothing on a standard report flags them.
Why underpayments are invisible
When a payer allows less than your contract says, the difference is usually posted as a contractual adjustment (often CARC CO-45). On the ledger the claim looks paid and closed.
Where underpayments hide in procedural billing
- Bilateral procedures paid as one side. A modifier 50 line allowed at 100% instead of the contracted bilateral rate (Medicare pays 150% for eligible bilateral procedures; commercial contracts vary).
- Multiple procedure reductions on the wrong line. The reduction should apply to the second and later procedures, ranked by value.
- Anesthesia time recalculated. Minutes rounded down or capped differently from the contract.
- Outdated fee schedules. A payer still paying last year's rates.
- Carve-outs ignored. Implants or drugs absorbed into a case rate.
A simple test
Pull 20 recent paid claims from your two largest commercial payers. For each line, compare the allowed amount with the rate in your contract or fee schedule. Any consistent gap is revenue you already earned.
| What to compare | Where to find it |
|---|---|
| Allowed amount | 835 remittance or EOB |
| Contracted rate | Payer contract or fee schedule exhibit |
| Payment rules | Contract sections on bilateral, multiple procedure, anesthesia |
Recovering underpayments
Most contracts allow a reconsideration within a set window. A successful request quotes the contract language, shows the expected calculation and lists the affected claims. Patterns (the same code underpaid every time) are best raised with the payer's provider relations team as well.
Related: underpayment recovery and AI underpayment detection.
This article is general billing information, not legal or coding-compliance advice. Payer rules, CPT descriptors and federal guidance change; check the current versions for your claims.