Claim Underpayments: How to Find and Recover Lost Revenue (2026)

By Ajay Pillai, CEO, Aayur Solutions· September 27, 2026· 10 min read

Why Underpayments Are Harder to Catch Than Denials

A denied claim is visible. It comes back with a code, sits in your worklist, and someone has to touch it before it goes away. An underpayment doesn't work that way. The claim processes, payment posts, the ERA closes out, and the shortfall disappears into your AR with nothing flagging it.

A practice getting shorted 6% on commercial claims doesn't see it in any one transaction. They see it at year-end when collections fall short of what the volume should have produced, and the cause rarely gets pinpointed.

What's actually happening: payers maintain internal fee schedules that don't always match the contracts they've signed. When you renegotiate a rate increase, someone at the payer has to manually load the new rates into their claims processing system. That step fails more often than payers will say out loud. Effective dates get entered wrong. Modifier-specific rates get missed. Carve-outs for specialty codes don't carry over. The payment looks right until you check it against the contract language.

How Much Are You Losing?

MGMA benchmarking puts underpayment losses at 5–7% of net revenue for small and midsize practices, rising to 7–11% of net revenue when unpaid claims are included. A 2025 MGMA Stat poll found that 48% of medical group leaders audit payer payments against contracted rates either monthly (30%) or quarterly. That means more than half are not doing it at all.

To put the revenue number in context: a practice collecting $3M annually losing 7% to underpayments is leaving $210,000 on the table every year. Paid. Closed. Filed. Just short.

The 5 Most Common Underpayment Patterns

1. Modifier 25 Bundling

Modifier 25 flags a significant, separately identifiable E&M service performed on the same day as a procedure. Payers look hard at Modifier 25 claims. The OIG has had Modifier 25 on its Work Plan for years, and payers use that history as justification to bundle the E&M into the procedure and pay only the procedure rate. If your documentation supports a separately identifiable E&M, that bundling is a contract violation.

This shows up most often in primary care and multi-specialty practices where a physician addresses a new or unrelated problem during the same visit as a minor procedure. Check any remittance line where a procedure code and an E&M both appear on the same date and compare what was paid against what the contract says for each code separately.

2. Multiple Procedure Reductions Applied Beyond Contract Terms

Most managed care contracts let payers apply a multiple procedure payment reduction (MPPR), which pays the second and subsequent procedures at a reduced rate, typically 50% under Medicare and most commercial contracts. The problem is payers sometimes apply MPPR to procedures that are contractually exempt, or they reduce add-on codes that should be paid at 100%. Neither is allowed under standard contract terms.

Pull any claim where three or more procedure codes appear on the same date of service. Compare the payment for each code against the fee schedule, then check whether the MPPR provisions in your specific contract cover those codes. PT, OT, chiropractic, and surgical specialties see this most often.

3. Wrong Rate After Contract Renegotiation

You negotiate a rate increase. The payer's contracting team signs off. Then somebody at the payer has to load the new rates into their claims processing system, and it doesn't always happen correctly or on time. Claims keep paying at the old rate for weeks or months after the new contract is effective.

If you renegotiated a contract in the last 12 months, pull your top 10 CPT codes and compare the paid amounts against your new fee schedule. Check the remittance date against your contract effective date. This is probably the single most recoverable underpayment category because the contract evidence is clean and the timeline is clear.

4. Facility vs. Non-Facility Rate Mismatch

Most CPT codes carry two rates: a facility rate for services at a hospital, ASC, or skilled nursing facility, and a non-facility rate for services at an office. Non-facility rates are higher because the provider is absorbing overhead the facility would otherwise cover. An underpayment happens when the payer pays the facility rate for a service rendered in a non-facility setting.

This typically traces to the provider's practice location being miscategorized in the payer's database, or place of service codes being mapped wrong on the payer's end. It's worth checking any claim where you billed POS 11 (office) and the paid amount looks low relative to your fee schedule.

5. Anesthesia Base Unit Errors

Anesthesia payment follows a formula: base units plus time units, multiplied by a conversion factor. Underpayments here almost always come from one of two places: the payer using the wrong base unit value for the procedure code, or applying a conversion factor that doesn't match the contract. Both are fixable with contract documentation.

Anesthesia underpayments tend to be large on a per-claim basis. They're worth running as a separate audit rather than catching them in a general remittance review.

How to Audit Your Remittances

Step 1: Start with one payer and 90 days

Don't try to audit all payers at once. Pick your highest-volume commercial payer and pull every remittance from the last 90 days. Export only the lines where payment posted, not denials, not adjustments written off. You need the CPT code, modifier, place of service, paid amount, and date of service for each line.

Step 2: Get your contracted fee schedule

Request a copy of your current contracted fee schedule from the payer's provider contracting department. If you don't have one on file, ask. Under nearly every managed care contract, you're entitled to a copy. Make sure you have the version with your effective date on it, not an older one from before a renegotiation.

Step 3: Compare at the line level

For each remittance line, look up the contracted rate for that CPT code and modifier combination. Flag anything paid more than 2% below the contracted rate. A small gap can be rounding. A consistent gap on the same code across multiple claims is a fee schedule loading problem, and it's recoverable.

Most practices find their first underpayment within the first 20 claims they review. That's not an exaggeration. The issue isn't whether they exist; it's how far back they go.

Step 4: Group by pattern before you file

Once you've flagged underpaid lines, group them: all Modifier 25 underpayments in one stack, all post-renegotiation wrong-rate claims in another, all MPPR overages in a third. Filing one dispute that covers 30 claims is far more efficient than filing 30 individual appeals, and payers take it more seriously when you present a pattern rather than a one-off.

How to File an Underpayment Dispute

Underpayment disputes go to a different department than denial appeals. Send them to provider relations or contract compliance, not the claims department. The documentation they need is also different.

Every dispute needs three things:

1. The specific EOB lines: claim number, date of service, CPT code, modifier, and what was paid
2. The contract language: the fee schedule page showing the correct rate for that code, with the effective date visible
3. The math: contracted rate minus amount paid, times the number of claims affected

With that documentation, the success rate on underpayment disputes runs 60–70% according to RCM specialists who track outcomes. Without the contract language, the number drops considerably. The payer has no obligation to take your word for what the contract says.

Watch your dispute deadline

Underpayment disputes have timely filing windows, just like initial claims. Most commercial contracts give you 90 to 180 days from the remittance date to file. Some go up to 12 months. Check your specific contract before assuming. Miss the window and the underpayment is almost certainly gone for good.

Building an Ongoing Audit Process

A one-time audit recovers historical losses. It won't stop new ones from building up.

The approach that works for most practices: flag any CPT code in your top 20 by volume that pays more than 5% below the contracted rate in a given quarter. That's a narrow enough scope to be manageable, and it catches fee schedule loading errors before they run for two years undetected. You don't have to review every line on every remittance to catch the money that matters.

Frequently Asked Questions

What is a claim underpayment in medical billing?

A claim underpayment occurs when a payer processes and pays a claim, but the amount paid is less than your contracted rate for that service. Unlike a denial, the claim is not rejected. It is paid, closed, and filed. The difference between what was paid and what your contract requires is an underpayment. MGMA benchmarking puts those losses at 5–7% of net revenue for small and midsize practices, rising to 7–11% when unpaid claims are included in the same bucket.

How do I find underpayments in my practice?

Start with one payer and pull all remittances for the last 90 days. Export every line where payment was made (not denied). Compare each paid amount against your contracted rate for that CPT code and modifier. Most practices find their first underpayment within the first 20 claims reviewed. Pay particular attention to Modifier 25 E&M claims, procedure bundles, and any claims submitted shortly after a contract rate increase.

What is the success rate for underpayment appeals?

With proper contract references and documentation, providers achieve a 60–70% success rate on underpayment disputes. The key is submitting the appeal with three items: the specific EOB line, the exact contract language showing the correct rate, and a calculation showing the dollar difference owed. Appeals submitted without the contract language have significantly lower success rates.

How long do I have to appeal an underpayment?

Timely filing windows for underpayment disputes vary by payer and are specified in your managed care contract. Most commercial payers allow 90–180 days from the date of the remittance to file a dispute. Some allow up to 12 months. Check your specific contract language. Missing the window typically makes the underpayment non-recoverable.

What is the difference between an underpayment dispute and a denial appeal?

A denial appeal argues that the claim should have been paid — the payer rejected it entirely. An underpayment dispute argues that the claim was paid, but at the wrong rate. They go to different departments at the payer and require different documentation. For underpayment disputes, the critical document is your managed care contract showing the correct contractual rate.