The Difference Between a Contractual Adjustment and an Underpayment

This distinction is where the money hides. A contractual adjustment is the difference between your billed charge and your contracted rate. If you bill $300 for a 99214 and your contracted rate with Payer X is $175, the $125 difference is a contractual adjustment. It is not revenue. You agreed to accept $175. An underpayment is when Payer X pays you $140 instead of $175. The difference — $35 — is money you are owed under your contract. It is not a contractual adjustment. It is a payment error. The problem: most practice management systems post both the contractual adjustment and the underpayment in the same transaction. The payment posts, the write-off posts, the balance zeros out, and the underpayment disappears into the contractual adjustment line without ever being identified separately. The only way to identify underpayments is to compare the actual payment to the contracted rate for that specific CPT code on that specific date of service with that specific payer. This comparison requires having your contracted fee schedule loaded into your practice management system — or doing it manually by pulling the EOB and comparing it to your contract. Most practices have their fee schedules in a file somewhere. Most have not loaded them into their billing system in a way that enables automated underpayment detection. That gap is where the 3 to 7 percent leakage lives.

Where Underpayments Cluster

Underpayments are not random. They cluster in predictable places. CPT codes with complex modifier rules. Services billed with modifiers — 25, 59, 91, bilateral procedure modifiers — are frequently underpaid because the payer's adjudication system applies a modifier reduction that is not consistent with your contracted terms. Your contract may specify full payment for a 25-modifier evaluation and management service performed on the same day as a procedure. The payer's system may apply a 50 percent reduction by default. Unless you audit, you will never know. Fee schedule updates that didn't apply retroactively. When a payer updates its fee schedule — typically January 1 — claims submitted in the transition period are sometimes processed under the old rate. If your new contracted rate is higher than the old rate and claims from January are processing at December rates, every one of those claims is an underpayment. The window to identify and recover them is typically 90 to 180 days from the date of payment, depending on your contract's payment dispute provisions. Anesthesia and time-based services. Services billed in time units — anesthesia, prolonged services, critical care — are systematically underpaid in practices where the time documentation is correct but the unit calculation on the claim is slightly different from the payer's calculation. A one-unit difference on a high-cost anesthesia service is a material underpayment. Across a month of anesthesia billing, small unit variances add up. Capitated vs. fee-for-service crossover claims. In practices with a mix of capitated and fee-for-service contracts, claims that cross over between payment models — services carved out of capitation and paid fee-for-service — are among the highest underpayment risk claims in the practice. The carve-out rules are contract-specific and the adjudication systems frequently apply the wrong payment model.

The Payment Audit Process

You do not need to audit every claim. You need to audit a statistically meaningful sample with enough frequency to detect systematic underpayment patterns. Monthly sample audit — 2 hours. Pull 25 to 30 paid claims from the previous month, weighted toward your highest-volume CPT codes and your highest-revenue payers. For each claim, compare the payment received to the contracted rate for that code with that payer. Document any variance. A variance of more than $5 on a sample claim gets flagged for investigation. Pattern identification. After two to three months of sample audits, you will have enough data to identify whether underpayments are random errors or systematic patterns. A systematic pattern — the same payer underpaying the same code by the same amount repeatedly — indicates an adjudication configuration error on the payer's side. Systematic errors are recoverable retroactively, often back to the date the error began. Recovery submission. Most payer contracts have a payment dispute provision that allows you to request review of a specific payment and submit documentation of the correct contracted rate. The dispute window is typically 90 to 180 days from the payment date — check your contract. Submit a payment dispute with the EOB, your fee schedule, and a calculation of the correct payment. Track every submission.

Your Action Item This Week

Pull your top five CPT codes by claim volume for the last 90 days. For each code, identify your contracted rate with your top three payers. Pull five paid claims per payer per code from the last 30 days. Compare actual payment to contracted rate. If you find a systematic variance — same payer, same code, consistent underpayment — you have found a recoverable underpayment pattern. Calculate the total dollar exposure across all claims for that code with that payer in the last 180 days. That is your recovery target. For the complete underpayment audit toolkit — fee schedule load template, sample audit framework, payment dispute letter, and payer-specific recovery tracking: [Payment Accuracy Playbook →](https://cleanclaimrx.com/library) Pay attention. Go get your money. — CleanClaimRx The Insider is published bi-weekly. For monthly industry macro analysis, read the [Insider Pulse](https://cleanclaimrx.com/pulse).