CPT 87804: Rapid Influenza Test Billing Guide (2026)

What Is CPT Code 87804?

CPT code 87804 reports a rapid influenza antigen test performed by immunoassay with direct visual observation, typically from a nasal or throat swab. It is a CLIA-waived point-of-care test that requires modifier QW on the claim, and it may be reported up to twice per encounter when the test differentiates influenza A and B and both results are documented separately.

CLIA-waived, QW required: 87804 is performed under a CLIA Certificate of Waiver, so every claim must carry modifier QW and the facility’s CLIA certificate number. Omitting QW is the single most common and most preventable 87804 denial across Medicare and most commercial payers.

Bill per antigen result: When a rapid flu test differentiates influenza A and influenza B and both results are documented, report 87804 twice on two separate claim lines, using modifier 59 on the second line to mark a distinct procedural service.

Reimbursed on the lab fee schedule: 87804 pays from the Clinical Laboratory Fee Schedule at a flat national rate of approximately $16 to $17 per test, with no professional or technical component split. When both flu A and B are reported, reimbursement roughly doubles.

Does CPT 87804 Require a Modifier?

Yes. CPT 87804 requires modifier QW for Medicare, Medicaid, and most commercial payers. Because 87804 is performed under a CLIA Certificate of Waiver, the claim must carry both the QW modifier on the code and the facility’s CLIA certificate number. Omitting QW is the single most common cause of 87804 denials, and it is entirely preventable with a clean charge capture setup.

Some private payers accept 87804 without QW, but many practices append it on every claim for uniformity, which is the approach the billing companies we vet overwhelmingly recommend. If the test is read on an automated analyzer or the lab holds a higher-complexity certificate, the QW requirement can differ, so confirm the certificate type on file before defaulting. Modifier 59 is a separate issue and applies only to the second unit when both flu strains are tested. The same CLIA-waived QW rule applies to the other core urgent care rapid test, the rapid strep test 87880.

One question we hear constantly from urgent care operators is whether the QW modifier should go before or after modifier 59 when billing two units. The answer varies by payer, but the standard practice is to bill the first line as 87804-QW and the second as 87804-59-QW, placing the distinguishing modifier first. Check with each payer’s claim submission guide, since some clearinghouses reorder modifiers automatically and others reject a line if the order does not match the payer’s expectation.

When Is 87804 Billed Twice for Influenza A and B?

Report 87804 twice only when the test yields separate results for influenza A and influenza B and the provider documents both. Bill the first unit as 87804-QW and the second as 87804-59-QW, where modifier 59 marks a distinct procedural service. If the test gives a single positive or negative result without differentiating A from B, report 87804 once. A medically unlikely edit (MUE) caps the code at two units per day.

Per CPT Assistant, when separate results are reported for different strains described by the same code, each result is coded separately and modifier 59 distinguishes them. Listing two units on a single claim line often causes the payer to ignore the second unit, so bill two separate lines. A few state Medicaid payers direct the use of modifier 91 instead of 59. Use modifier 91 only with written payer instruction, since it contradicts CPT guidance and applying it without documentation invites a follow-up audit.

Across the billing companies we vet, a recurring pattern separates the groups that collect cleanly on flu tests from those that leave money on the table: the strong operators build the A-and-B two-line rule directly into charge capture templates, so the second unit auto-populates with modifier 59 whenever the test result differentiates. The weak operators leave it to manual entry, and the second unit gets missed at volume, especially during flu-season surges when every minute at the front desk counts.

What Is the Difference Between CPT 87502 and 87804?

Both codes test for influenza, but they use different technology, which drives the coding, complexity, and payment. Understanding the distinction matters because substituting one for the other is a coding error that payers will deny outright.

87502 covers the first two influenza types or subtypes by nucleic acid detection. 87804 is the rapid antigen test. Do not substitute one for the other. Code the methodology actually performed and documented. In our experience matching providers with billing partners, molecular test claims billed as 87804 or vice versa are among the fastest denials payers issue, because the CLIA certificate level and the test methodology must match the CPT code on the claim.

What Diagnoses Support CPT 87804?

Medicare and commercial payers reimburse 87804 when the record documents an influenza-like illness or a clinical reason to test, not for asymptomatic screening. Representative supporting ICD-10 codes are listed below, but the exact payable list is set by each payer’s local coverage determination, so confirm the covered diagnoses with the specific payer before billing.

The most common issue we see providers run into with 87804 denials is linking the test to a screening diagnosis or an asymptomatic visit code. A flu test ordered without a documented symptom or clinical indication will not pay under Medicare or most commercial plans, regardless of how clean the rest of the claim is. Providers often come to us after a batch of flu-season denials, and the root cause is almost always a diagnosis code problem, not a modifier problem.

CPT 87804 Reimbursement and Fee Schedule

87804 is paid from the Clinical Laboratory Fee Schedule (CLFS), not the Physician Fee Schedule, so there is no professional or technical component and no modifier 26 or TC. Medicare sets a national limitation amount that the contractors apply, and the approximate national rate has run about $16 to $17 per test. When a differentiated test reports influenza A and B as two units, the reimbursement roughly doubles because each unit is paid separately. Commercial rates vary by contract and Medicaid varies by state. Because the fee schedule updates annually, verify the current CLFS amount before relying on any specific figure.

One detail that surface-level guides miss is the relationship between the CLFS rate and the contracted rate on commercial plans. Many commercial payers benchmark their lab fee schedule to a percentage of Medicare’s CLFS, so a practice that knows its Medicare rate can estimate its commercial reimbursement with reasonable accuracy. Practices that track this ratio across their top five payers can spot underpayments quickly at posting, which is the kind of operational intelligence a good billing partner builds into the workflow.

Understanding how your E/M visit codes like 99214 interact with lab codes on the same encounter also matters, since the E/M and the lab test are separately billable but the documentation must support both.

What Changed for CPT 87804 in 2026?

Effective January 1, 2026, CMS introduced CPT 87812 for visually read COVID-19 and influenza A and B combination tests. For a single manual combo strip that reads both COVID-19 and flu, report 87812 rather than billing 87811 and 87804 together, which was the prior practice and is now an unbundling risk. Standalone flu-only rapid tests still use 87804.

This change matters more than it looks. During the 2024 and 2025 flu seasons, many urgent care sites routinely billed 87811 (COVID rapid) plus 87804 (flu rapid) when using a single combination test device. That was the correct approach before 87812 existed. As of 2026, a claim that still bills both codes for a single combo strip is an unbundling error that CMS and commercial payers will flag. Update the chargemaster so combo devices map to 87812 and single-analyte flu tests map to 87804.

This is exactly the type of regulatory change that gets missed when nobody is watching the annual code updates. Across the billing companies we vet, the ones that caught the 87812 transition early updated their charge capture templates before flu season hit. The ones that did not are now working denials. That pattern holds for other recent Medicare changes, including the proposed 2027 Medicare conversion factor cut that affects urgent care reimbursement broadly.

Top Reasons CPT 87804 Claims Get Denied

Most 87804 denials come from a short list of avoidable errors. Fix these before submission and the code collects cleanly at volume.

• Omitting the QW modifier. A CLIA-waived flu test billed without QW is rejected by Medicare and most payers almost immediately.
• Missing the CLIA certificate number. The claim must carry the facility’s CLIA number along with the QW modifier. Without it, even a correctly modified claim gets denied.
• Billing two units without modifier 59. A second flu unit for A and B needs 87804-59-QW on a separate line, or the payer ignores or denies the second unit.
• Reporting twice for a non-differentiating test. A single combined positive or negative result should be billed once, not twice. Overcoding here triggers audits.
• Coding a screening test. An asymptomatic screening flu test without a covered indication is not payable under Medicare or most commercial plans.
• Unbundling a combo device in 2026. Billing 87811 plus 87804 for a single COVID-and-flu combo strip should now be reported as 87812.
• Wrong place of service. An urgent care site using the wrong POS code alongside the lab test creates a downstream denial, even when the lab code itself is correct.

Frequently Asked Questions

Next Steps

New to urgent care coding? Start with the CPT 99281 guide to understand why urgent care visits use different E/M codes than the emergency department.

Billing the rapid strep test too? The QW modifier and CLIA rules that apply to 87804 also apply to the rapid strep test, CPT 87880. The same charge capture logic covers both.

Coding upper respiratory visits? See the J06.9 coding and billing guide for the diagnosis code that most often supports rapid flu and strep testing in urgent care.

Watching the 2027 fee schedule? The 2027 Medicare conversion factor cut affects E/M reimbursement for the same visits where these lab tests are performed.

Ready to hand billing off? Get matched with vetted urgent care billing companies that build the QW modifier and the A-and-B rules into charge capture so nothing slips at volume.