Specialty Pharmacy Billing Trends to Watch in 2026

Specialty pharmacy now accounts for more than half of total U.S. drug spend despite representing under 2% of prescriptions. For practices that buy and bill specialty drugs, 2026 brings a wave of changes, from white bagging mandates to biosimilar substitution rules, that will directly affect reimbursement.

White and Brown Bagging Mandates Are Expanding

White bagging, where a specialty pharmacy dispenses a drug directly to a provider's office for a specific patient, rather than the practice buying and billing it, has been growing for years, but 2026 marks a turning point. More payers are mandating white or brown bagging for high-cost infusion drugs, particularly in oncology and rheumatology, as a cost-containment measure.

For practices accustomed to buy-and-bill economics, this shift removes a meaningful revenue stream: the spread between acquisition cost and reimbursement on drugs that often represented 20-40% of practice margin on infusion visits. Practices need updated workflows for receiving, storing, and verifying third-party-supplied drugs, plus careful tracking to ensure waste and partial-vial billing (JW/JZ modifiers) are still captured correctly even when the practice didn't purchase the drug.

Biosimilar Substitution Rules Are Tightening

With over 50 biosimilars now approved by the FDA across oncology, rheumatology, and ophthalmology, payers are increasingly requiring biosimilar-first protocols, meaning a reference biologic claim may be denied or down-coded unless a biosimilar was tried first or a medical exception is documented. CMS has continued to push biosimilar adoption through reimbursement incentives, with ASP+8% rates for biosimilars compared to ASP+6% for reference products under certain Medicare Part B policies.

Practices that haven't updated their formulary preference workflows risk a growing share of denials tied to "non-preferred product" determinations. The fix is procedural: build biosimilar-first defaults into ordering workflows, and ensure medical necessity documentation for reference-product exceptions is captured at the point of order, not after a denial.

J-Code and HCPCS Updates Continue Their Annual Churn

HCPCS Level II code updates for specialty drugs happen quarterly, and 2026 has already introduced new permanent J-codes for several drugs that previously billed under miscellaneous codes (J3590, J9999, J7999). Billing under miscellaneous codes typically triggers manual review and slower payment, average miscellaneous-code claims take 18-25 days longer to adjudicate than claims with permanent J-codes, according to clearinghouse benchmarking data.

Practices that don't update their charge masters promptly after quarterly HCPCS releases risk both delayed payment (continuing to bill miscellaneous codes after a permanent code exists) and denials (billing a deleted code after its replacement takes effect). A quarterly charge master audit cadence, tied to CMS's HCPCS release calendar, is now a baseline requirement for specialty billing teams.

340B Scrutiny and Site-of-Service Differentials

340B drug pricing program audits have intensified, with manufacturers increasingly restricting contract pharmacy arrangements and payers applying differential reimbursement for drugs administered at 340B-covered sites. Practices operating under 340B, common among hospital-affiliated specialty clinics, need claim-level modifiers (such as the "JG" or "TB" modifiers for Medicare) to correctly identify 340B-acquired drugs, and failure to apply them correctly is now a recurring audit finding.

Site-of-service differentials are also widening: payers increasingly reimburse the same infusion drug at a lower rate when administered in a hospital outpatient department versus a physician office, with differentials of 15-30% reported across major commercial payers. Practices with multiple sites of service need billing systems that apply the correct fee schedule per location automatically, manual site-of-service tracking is a growing source of underpayment.

What Specialty Practices Should Do Now

• Audit payer policies quarterly for white/brown bagging mandates and biosimilar-first requirements specific to your top five payers by volume.
• Build a charge master update cadence aligned to CMS's quarterly HCPCS release schedule, with a designated owner for specialty drug codes.
• Document medical necessity for reference-product use at the point of ordering, not retroactively after a biosimilar-preference denial.
• Verify 340B modifier accuracy on every applicable claim, this is now a top audit target for both manufacturers and payers.
• Track site-of-service fee schedules separately for each location, especially for practices with both office-based and hospital-affiliated infusion sites.

The Bottom Line

Specialty pharmacy billing in 2026 rewards practices that treat policy monitoring as an ongoing operational function rather than an annual compliance exercise. The practices losing the most revenue this year aren't the ones facing new mandates, they're the ones still billing under last year's codes and formulary assumptions.