Underpayment Recovery in Medical Billing

Introduction

Underpayment recovery means comparing what a payer actually paid against what the contract supports, then pursuing the difference when it's valid. That sounds simple. In practice, it's one of the most misunderstood parts of revenue cycle management.

This guide is written for US infectious disease physicians, independent ID practices, group leaders, and practice administrators. Getting reimbursement right matters more here than in many specialties, because OPAT, infusion, and buy-and-bill services carry real drug acquisition costs and authorization requirements that general billing teams often miss.

Here's the core problem: a claim marked "paid" in your system can still be wrong. No rejection flag, no alert, nothing obviously broken. Just a quiet shortfall sitting in a closed account.

This article walks through how to detect these gaps, validate them, pursue recovery when justified, and prevent them from recurring.

Key Takeaways

• An underpaid claim is paid below the contracted or supported amount; not every variance is recoverable
• Recovery depends on checking contracts, fee schedules, coding, and documentation, not just a variance report
• The core workflow is Detect, Validate, Recover, Resolve, in that order
• OPAT, infusion, and drug administration claims deserve extra scrutiny because errors repeat at volume
• Use your own claims data, not industry benchmarks, to decide where to focus

What Is Underpayment Recovery in Medical Billing?

Underpayment recovery is the structured process of spotting a short payment, determining whether it conflicts with your contract or an applicable reimbursement rule, and seeking correction through the payer's own process. That middle step, confirming the shortfall is real, is where most practices skip ahead and lose credibility with payers.

According to HFMA's revenue cycle guidance, underpayments are measured against the calculated or contracted payment, not against billed charges. If you compare payments to your charge sheet instead of your actual contract, you'll flag discrepancies that aren't real.

Underpayment Isn't the Only Explanation for a Short Payment

A lower-than-expected payment could be several different things, and each demands a different response:

• Underpayment - paid below the contracted or supported amount
• Contractual adjustment - the negotiated rate reduction you already agreed to
• Patient responsibility - deductible, copay, or coinsurance shifted to the patient
• Denial - rejected or unpaid, usually carrying its own denial code
• Payment delay - still in adjudication, not yet finalized
• Overpayment - paid above what's owed, which triggers a repayment obligation instead

Treating all six as the same problem is how practices waste appeal effort on claims that were never underpaid in the first place.

The goal is accurate payment for services already rendered, better visibility into where revenue leaks, and fewer repeat mistakes going forward.

Why Underpayment Recovery Matters for Infectious Disease Practices

Smaller and independent practices feel these gaps more acutely than large health systems do. When your billing team is two or three people instead of twenty, one missed underpayment pattern can run for months before anyone notices.

Infectious disease also generates many repeating claim types: OPAT episodes, infusion administration, drug charges, and follow-up visits. A single coding or contract error can replicate across dozens of claims before it's caught.

Where ID-Specific Review Points Hide

Several areas deserve routine attention, though the exact coding and payer rules should always be verified against current guidance rather than assumed:

• OPAT episode billing - drug and administration components are often billed and adjudicated separately
• Infusion and administration services - initial versus subsequent service codes get misapplied more often than you'd expect
• Drug and supply charges - unit and NDC mismatches are a recurring root cause
• Place-of-service differences - home infusion and office administration are reimbursed differently
• Authorization and medical-necessity requirements - these vary by payer and by specific agent

Internally, this pattern shows up constantly: a drug claim paid below the contracted rate produces no rejection and no alert. Without a loaded fee schedule to compare against, the error is invisible. It just sits there as a short-pay, indistinguishable from a correctly paid claim until someone runs the comparison.

MGMA's 2025 poll of 193 medical group leaders found that 48% audit payer payments against contracted rates monthly or quarterly. That figure measures how often practices check, not how much money is typically lost.

Don't accept a generic "X% of revenue is lost to underpayments" claim. No credible ID-specific study backs that number, and your own data will tell you more than a benchmark ever could.

Left unresolved, these gaps don't just cost revenue. They distort your service-line economics, weaken your position at contract renewal, and create repeat work every time the same error recurs.

How Underpayment Recovery Works

The flow runs from service delivery through claim submission, remittance posting, payment comparison, validation, correction, follow-up, and feeding findings back into your workflows. Here's how each stage actually works.

Step 1: Detect

Detection starts with assembling the right data: claims, ERAs/EOBs, payment postings, current contract versions, fee schedules, payer policies, adjustment codes, and yes, zero-balance accounts. A closed claim with a zero balance looks finished. It isn't necessarily correct.

Basic variance reports have real limitations:

• Rely on contract data that may not be fully or correctly loaded
• Use expected-payment logic that can be outdated or wrong
• Miss charge or coding detail that skews the comparison
• Treat posting errors as payer errors
• Miss documentation or workflow issues that caused the shortfall

Loading contracted rates into your system is one of the highest-impact single moves a practice can make. Without that step, a below-contract drug payment is simply undetectable, no matter how good your billing team is.

Step 2: Validate

Before you escalate anything, run through a validation checklist at the claim level:

• Payer and plan match
• Date of service, provider, and location are correct
• Codes, modifiers, and units are accurate
• Drug or supply identifiers (NDC) match what was administered
• Authorization was in place and current
• Billed and allowed amounts align with the fee schedule version in effect
• Remittance reason codes make sense
• Timely-filing deadline hasn't passed

This step is where you separate a true payer underpayment from an internal coding error, a legitimate lesser-of provision, patient responsibility, a secondary-payer issue, or an overpayment that actually needs to go back.

Step 3: Recover and Resolve

Prioritize by dollar value first, not claim count. In a drug-heavy practice, one high-value infusion claim can outweigh an entire month of office visits. Rank by:

1. Dollar value of the discrepancy
2. Claim age and remaining filing deadline
3. Whether it's part of a recurring payer or code pattern
4. Documentation readiness
5. Expected effort to pursue it

A contract-anchored appeal needs specific components:

• Claim identifiers
• Expected versus received payment with the exact calculation
• Contract or fee-schedule language supporting your position
• Relevant remittance detail
• Clinical or billing documentation
• The requested correction and a way to track the payer's response

Close the loop every time. Record the outcome, the root cause, the recovered amount, and how long it took. That root-cause data is what tells you whether the fix belongs in coding, charge capture, authorization, payment posting, or your next contract negotiation.

Where Recovery Applies and What Affects Results

Recovery work touches the systems you already run day to day:

• EHR or practice management system
• Clearinghouse and ERA/EOB posting
• Contract repository and A/R work queues
• Coding review and payer portals

It typically surfaces during post-payment claim review, zero-balance audits, recurring OPAT or infusion reconciliation, drug and administration payment checks, contract renewal analysis, or a retrospective audit.

Common Review Triggers

• Unexpected payment variance on a specific code
• Payment repeated at an outdated rate
• Unexplained bundling or missing modifier impact
• A pattern affecting the same code or service line repeatedly
• Contract amendment or payer policy change

What Actually Affects Your Results

Whether recovery efforts succeed depends on:

• Contract and fee-schedule quality - current effective dates, complete rate exhibits, carve-outs, escalators, and lesser-of language
• Claim and clinical data quality - accurate coding, units, modifiers, NDC information, and timely submission
• Operational capacity - staff expertise, work-queue design, and clear ownership of open disputes
• Practice-specific complexity - recurring OPAT episodes, buy-and-bill economics, multiple locations, and shifting payer plans
• Compliance controls - separate underpayment recovery from overpayment handling; involve compliance or legal review when contract language is genuinely disputed

Administration coding deserves a closer look. CMS's NCCI manual identifies codes 96360-96379 for hydration, therapeutic, and diagnostic infusions, with 96365 as the initial service and 96366 for each additional hour.

Normally only one initial service applies per encounter unless separate IV access sites are medically necessary, and office-based administration codes don't carry over to facility billing. Getting this distinction wrong is a common source of recurring variance.

GrowInfectiousDisease's free, ungated resource hub can help practices run these numbers with their own figures, using browser-based tools and plain-English explainers, though it doesn't file payer appeals or guarantee recovery outcomes.

Common Issues, Misconceptions, and When Recovery May Not Be Appropriate

Two misconceptions drive a lot of wasted recovery work:

• Any payment below the billed charge is an underpayment. It isn't. Compare against the contracted or otherwise applicable amount, not your charge master.
• A paid or zero-balance claim is automatically correct. Posting workflows and automatic contractual adjustments can bury unresolved differences without anyone noticing.

A variance report is a lead, not a conclusion. It can't replace contract review, coding expertise, or human validation. Feed it bad inputs, like an outdated fee schedule, and you generate false positives. That wastes appeal effort on claims that were never underpaid.

Pursuing recovery isn't always the right call. Skip it when:

• The payment actually matches the contract once you check closely
• The balance is legitimate patient responsibility
• You're past the appeal or timely-filing window
• Documentation can't support your position
• The amount falls below your practice's own pursuit threshold
• It turns out to be an overpayment, which needs a different process entirely

Document why you didn't pursue a variance. When a workflow or contract change may be warranted, judge recurring patterns across claims, not one isolated low-value discrepancy.

Conclusion

Underpayment recovery is a contract- and evidence-based process, not a blanket search for every gap between charges and payments.

Infectious disease practices improve financial visibility when they:

• Review both paid and zero-balance claims
• Validate recurring OPAT and infusion payments
• Prioritize variances that are actually worth pursuing
• Feed findings back into coding, authorization, and contract decisions

Accurate application beats blind automation or borrowed benchmarks every time. Use your own claims data. For disputed contractual, compliance, or legal questions, bring in qualified professional advice rather than guessing.

Frequently Asked Questions

What is an underpaid claim?

An underpaid claim is one paid below the contracted or otherwise supported reimbursement amount. A lower payment isn't an underpayment until you verify it against the contract and claim details.

How is an underpayment different from a denial?

A denial means the claim was rejected or left unpaid and usually carries a denial code. An underpayment is processed and paid, just for less than what's owed. Each needs a different recovery workflow.

How can a medical practice identify underpaid claims?

Compare payments against the contract, review ERAs and EOBs closely, audit zero-balance accounts, validate the fee schedule version in use, and check coding, documentation, and payer-specific rules.

What documentation is needed to appeal an underpayment?

You'll need claim and remittance details, the relevant contract or fee-schedule language, your expected-payment calculation, coding or clinical support, authorization evidence if needed, and proof the appeal is timely.

Are all payment differences recoverable?

No. Recoverable payer errors are different from legitimate contractual reductions, patient responsibility, your own billing mistakes, noncovered services, missed deadlines, or situations that are actually overpayments.

How can infectious disease practices prevent repeat underpayments?

Keep contract data current, get coding and charge capture right the first time, reconcile OPAT and infusion claims regularly, assign clear staff ownership, and feed trend findings back into contract and workflow decisions.