A payment below the billed charge is not automatically an underpayment. A medical practice should compare the payer’s allowed amount with the applicable contract, service date, procedure code, modifiers, place of service, and remittance adjustments. Only after reconciling those elements can the practice determine whether a correction, contractual dispute, or formal appeal is appropriate.
Start with the actual payment record
Retrieve the original claim, payer acknowledgment, electronic remittance advice or paper remittance, and the posted patient ledger. Identify each service line rather than comparing only the claim total. A remittance can include multiple claims and line-level adjustments, so the deposit amount alone rarely explains a discrepancy. Match the payer claim control number to the original submission and identify any corrected or replacement claim.
Determine which rate actually governs
Find the signed participating-provider agreement and the fee schedule or amendment effective on the date of service. Check whether a delegated network, leased network, specialty arrangement, or location-specific schedule applies. An insurer’s published fee schedule is not necessarily the rate promised in a particular contract. For a percentage-of-Medicare contract, document the relevant Medicare schedule year, locality, setting, code, and any applicable modifiers rather than relying on an undated online calculator.
Separate adjustments from errors
Compare billed charge, allowed amount, contractual adjustment, payer payment, patient responsibility, and any recoupment. CMS explains that remittance group codes distinguish contractual obligations from patient responsibility. Do not automatically bill the patient for a disputed contractual difference: verify the agreement and applicable balance-billing protections first. A zero-dollar line can reflect bundling, duplicate adjudication, coverage exclusion, or another reason; the adjustment and remark codes are starting points, not the final explanation.
Build a reproducible underpayment calculation
For each affected line, create columns for service date, CPT/HCPCS code, units, modifier, place of service, contractual allowed amount, payer allowed amount, patient share, payment received, and difference. Attach the contract provision or fee-schedule page supporting the expected rate. If the insurer has offset an earlier overpayment, document that separately. Keep protected health information in an access-controlled system rather than an unsecured spreadsheet.
Request a specific correction
Ask the payer to identify the pricing methodology and contract version used, explain each disputed adjustment, and provide a claim-level reference number. Submit a corrected claim only if the original billing information was wrong; if the claim was correctly submitted but priced incorrectly, use the payer’s reconsideration or provider-dispute channel. Confirm the applicable contractual filing limit and keep submission receipts.
Prevent repeat errors
Track underpayments by payer, contract, procedure, location, and cause. Repeated mismatches may indicate a fee-schedule load issue, incorrect provider affiliation, or a configuration problem. Audit a small sample before escalating a systemic allegation. Patients should receive a corrected statement if their share changes; practices should not convert unresolved payer disputes into unsupported patient balances.
Practical next step
Start with a dated written request and keep the reply with the original records. For a related practical example, see this Did They Pay? accountability guide. The CMS guidance on remittance advice and adjustment codes provides additional official guidance; apply the rules of the particular payer and coverage arrangement.
Frequently asked questions
Is every payment below charges an underpayment?
No. Charges and contractually allowed amounts are different figures; compare the actual agreement and remittance.
Should the practice send a corrected claim?
Only when the submitted claim needs correction. A pricing dispute on an accurate claim may require reconsideration instead.
Can the patient be billed for the difference?
Not automatically. Contract terms and applicable protections must be checked before transferring any balance.