Alt text: Illustration of a bar chart showing a gap between expected and paid amounts on insurance claims
A mental health group renegotiates its contract with a regional payer and secures higher rates for psychotherapy codes starting in January. By spring, the office manager notices that collections have not changed much. A closer look shows the payer is still paying the old rates. Every claim was marked «paid,» so nothing triggered a follow-up. Four months of underpayments have already accumulated.
Denials are visible because claims come back unpaid. Underpayments are different. The money arrives, the claim closes, and the shortfall disappears into the routine of posting payments. Identifying insurance underpayments requires a deliberate process that compares what was paid against what should have been paid.
Why Underpayments Slip Past Most Billing Teams
Most practice management systems are built to flag denials, not short payments. Payment posting teams are measured on speed and accuracy of posting, not on whether the allowed amount matches the contract.
Underpayments tend to come from a few recurring sources:
- Fee schedule errors on the payer’s side, such as rate updates that were not loaded or were applied to the wrong provider or location
- Incorrect contract interpretation, including how the payer applies multiple procedure reductions or modifier-based reductions
- Place-of-service mismatches, where a service is paid at a facility rate instead of the non-facility rate
- Bundling and edit issues where a separately payable service is folded into another
- Coding problems on the practice side, such as missed modifiers or under-coded visits, that reduce payment even when the payer processes correctly
Practices that want to address both payer and internal causes can find more detail in this guide to fixing billing errors and underpayments.
Behavioral health and specialty practices can be especially exposed. Time-based psychotherapy codes, add-on codes, and services with modifier-specific rates create many opportunities for a payer’s system to apply the wrong rate. Because each individual difference may be small, the losses build quietly across hundreds of sessions each month.
Start With Accurate Expected Payment Data
An underpayment cannot be identified without knowing what the payment should have been. That requires the practice to have its contracted fee schedules loaded into its billing system or a separate tracking tool.
A dependable foundation includes:
- A current copy of every major payer contract and its fee schedule
- Expected allowed amounts loaded by CPT code, modifier, and place of service
- Notes on contract terms that affect payment, such as percentage-of-Medicare methodologies, multiple procedure rules, and annual escalators
- A schedule for updating expected amounts when contracts renew or Medicare rates change
Many practices find this step harder than expected because contracts are stored in different places, some fee schedules were never provided, and terms reference external rate sets. Requesting a complete fee schedule from each payer is often the first task.
For practices without dedicated contract management software, even a spreadsheet listing the top 20 to 30 CPT codes by volume for each major payer, with expected allowed amounts, is a meaningful start. Those codes typically account for most of the practice’s revenue, so they are where underpayments matter most.
Read the Remittance, Not Just the Payment Amount
The electronic remittance advice, or 835 file, explains why a payment was reduced. Claim adjustment reason codes and remark codes tell the story, but they are often posted without review.
Some codes deserve particular attention:
- CO-45 indicates charges exceed the fee schedule or contracted amount. It is expected on most claims, but the adjusted amount should match the contract. A detailed explanation is available in this breakdown of the CO-45 denial code.
- CO-253 reflects the Medicare sequestration reduction, which is a legitimate adjustment and not an underpayment.
- CO-59 and similar codes related to multiple procedure or bundling rules should be checked against the contract’s actual terms.
Setting up variance reports that compare the allowed amount on each ERA line with the expected allowed amount makes underpayments visible automatically. Even a simple threshold, such as flagging any line where the allowed amount falls below the expected amount by more than a small margin, can surface patterns quickly.
Secondary payments need the same attention. When a secondary payer processes a claim, its payment depends on the primary payer’s allowed amount and its own coordination of benefits rules, and errors at either step can leave balances that are incorrectly transferred to the patient.
Payment posters should also have a clear escalation path. When they notice an unusual adjustment while posting, they need to know who reviews it and how to flag the claim, so the observation does not get lost in the next batch of payments.
Look for Patterns, Then Dispute in Batches
Individual underpayments are often small, which is why they are easy to ignore. Patterns are where the real dollars are. A rate update missed for one CPT code across one payer may affect hundreds of claims.
When reviewing variance reports, group findings by:
- Payer and product line
- CPT code and modifier
- Rendering provider and location
- Date range, which helps pinpoint when a problem started
Once a pattern is confirmed, a single organized dispute covering all affected claims is usually more effective than separate appeals. Payer contracts often specify how and within what timeframe payment disputes must be submitted, so tracking those deadlines is important. Escalating to the payer’s provider relations contact with a clear summary of affected claims and expected amounts tends to speed resolution.
Keep a record of every dispute, including the date submitted, the claims involved, the amount in question, and the outcome. That history becomes valuable leverage during the next contract negotiation, since it shows the payer exactly how often its processing fell short of the agreed terms.
Close the Loop Internally
Not every variance points to a payer error. Sometimes the practice’s own coding or billing caused the reduced payment. Reviewing internal causes is just as important.
Separating payer-caused variances from practice-caused variances also keeps disputes credible. A payer that receives a dispute for an underpayment the practice caused is likely to treat future disputes with more skepticism.
- If modifiers are regularly missing, coders may need targeted training or claim edits.
- If visits are consistently coded below what documentation supports, providers may need education on E/M leveling.
- If place-of-service codes are wrong, scheduling or charge entry workflows need adjustment.
Building underpayment review into the monthly routine, rather than doing it once a year, prevents months of shortfalls from building up. Practices without the time or tools to run this consistently often bring in outside help. To see how this works in practice, many look at billing partners that include payment variance review in their services.
The Takeaway
Identifying insurance underpayments starts with knowing what each payer owes, then comparing every payment against that expectation. Load accurate fee schedules, read remittance codes closely, look for patterns across claims, and dispute in organized batches. Over time, this process recovers revenue that would otherwise go unnoticed and keeps payer contracts working the way they were negotiated.