Underpayments: the leak an expected-pay table catches

How do you actually spot an underpayment against your fee schedule?

You spot an underpayment by comparing what a remittance actually paid against what you expected it to pay for that code, that payer, and that date of service — not by noticing that a number looks low. Without a standing expected-pay table, a genuine shortfall and a routine contractual adjustment look identical on the page, and the shortfall wins by default because nobody checked.

Building that table starts with an anchor number for every code you bill, and the cleanest public anchor is Medicare's own rate: CMS publishes a Physician Fee Schedule look-up tool giving the national and locality payment amount, RVUs, and payment indicators for any CPT or HCPCS code 1Ref 1Centers for Medicare & Medicaid Services (2026).Physician Fee Schedule Search.That CMS publishes a public Physician Fee Schedule look-up tool where any clinician can find the national and locality payment amount, RVUs, and payment indicators for a CPT/HCPCS code, used here as the anchor number for an expected-pay table.. Pricing off Medicare — using its published rate as the reference point even for commercial claims — gives you one stable number to compare every payer's actual payment against.

Build the table before you go looking for gaps

Your fee schedule is the actual contracted or expected amount per code per payer; the Medicare Physician Fee Schedule is only the anchor you build it around, since the Medicare rate is updated annually through rulemaking and is public, unlike most commercial contracted rates 2Ref 2Centers for Medicare & Medicaid Services (2026).Physician Fee Schedule.That the Medicare Physician Fee Schedule sets payment for clinician services and is updated annually through rulemaking, used here to explain why it is a public, checkable anchor while most commercial contracted rates are not. As of July 2026.. The table itself is nothing more than expected pay by code by payer, one row per combination, and it should be updated whenever a contract renews or a fee schedule is renegotiated — a table built once and never revisited becomes exactly the blind spot it was supposed to prevent.

Once the table exists, every remittance answers one question instead of raising a vague feeling: billed, allowed, paid — does the allowed amount match what the table expected, and does the paid amount match the allowed amount after any patient-responsibility split? A mismatch at either step is worth a closer look before it's dismissed as normal variation.

Rule out the two adjustments that only look like underpayments

Not every lower-than-expected payment is a mistake. NCCI procedure-to-procedure edits and Medically Unlikely Edits define specific code pairs and unit limits that Medicare — and payers who follow similar logic — will not pay together or above a capped quantity, and the edit files behind these rules are public and checkable by code 3Ref 3Centers for Medicare & Medicaid Services (2026).NCCI for Medicare.That NCCI procedure-to-procedure edits and Medically Unlikely Edits define which code pairs and unit counts will not be paid together, and that the edit files are public, used here to distinguish a legitimate bundling reduction from a real underpayment.. A claim reduced by a bundling edit isn't underpaid; it's paid according to a rule you can look up and confirm.

The way to tell the difference is the same reading discipline every remittance rewards: check the Claim Adjustment Reason Code and the Remittance Advice Remark Code together before assuming a gap is an error 4Ref 4X12 (2026).Claim Adjustment Reason Codes.That CARCs are the standard X12 code list explaining why a claim or service line was paid differently than billed, used here to check whether a lower payment is explained by a legitimate edit or reason.5Ref 5X12 (2026).Remittance Advice Remark Codes.That RARCs supply the supplemental detail beyond the CARC on a remittance, used here alongside the CARC to confirm the specific reason behind a reduced payment.. A CARC pointing to a bundling or unit-limit edit closes the question. A CARC that doesn't name a legitimate edit, paired with a paid amount below your table's expected number, is the real signal worth chasing.

Know which rulebook applies before you dispute the gap

What counts as the correct payment depends on which type of plan you're dealing with, and that changes where the dispute goes. Self-funded employer plans are governed by ERISA rather than state insurance law, and ERISA sets its own claims framework for those plans — which is why a state prompt-pay statute you might expect to apply sometimes doesn't reach a self-funded plan at all 6Ref 6U.S. Department of Labor (2026).ERISA.That self-funded employer plans are governed by ERISA rather than state insurance law, which is why state prompt-pay and assignment laws often do not reach them, used here to explain why the applicable underpayment rule depends on plan type.. Confirm the plan type before assuming a general rule governs a specific underpayment.

Load the table into your workflow so the check runs itself

The expected-pay table only catches underpayments if the comparison actually happens on every claim, which means loading allowables into whatever system posts your remittances rather than keeping the table in a separate spreadsheet nobody opens. CAQH CORE's operating rules standardize the eligibility, claim-status, and remittance transactions payers are required to support, which is part of what makes an automated posted-versus-expected comparison workable even for a practice with no dedicated billing staff 7Ref 7CAQH (2026).CAQH CORE Operating Rules.That CAQH CORE operating rules standardize the eligibility, claim-status, and ERA/EFT transactions payers must support, used here as what makes an automated posted-versus-expected payment comparison workable for a solo practice..

A weekly review of flagged mismatches — not a monthly one, and not "whenever something looks off" — is what turns the table from a reference document into an actual detection system. The cost of underpayment detection isn't the table; it's the discipline of checking it against every remittance instead of only the ones that catch your eye.

What to do once the table finds a real gap

A confirmed underpayment — a paid amount below your table's expected number, with no bundling edit or documented contractual reason explaining the difference — is a dispute worth raising with the payer directly, referencing the specific contracted or benchmark rate the table expected. Treat one flagged claim as information first: check whether the same code and payer combination shows the same gap on other recent remittances before deciding whether this is a one-time posting error or a systemic repricing problem.

A gap that only ever shows up once is often resolved with a phone call and a corrected remittance. A gap that recurs across many claims for the same code and payer is worth raising at the contract level, because the table that caught it once will keep catching it every week until the underlying rate is fixed.