You signed a contract promising 100% prescription drug rebate pass-through. Your CFO smiled. Your consultant nodded. And a few months later, the check arrived. But no one told you the biggest threat to actually keeping those savings isn’t the contract language, the PBM’s fine print, or even the pharmacy benefit manager themselves. It’s the software that sits between your employees and your claims data. Your benefits administration platform.
After spending over a decade auditing employer plans and the systems that support them, I’ve uncovered a pattern that rarely gets discussed in the benefits world. Rebate pass-through isn’t a pricing issue. It’s a data architecture problem. And if your HRIS, enrollment system, or third-party administrator wasn’t built to handle pharmacy rebate data at the individual employee level, you’re leaving savings on the table, often without any idea it’s happening.
Three Hidden System Traps That Kill Pass-Through
Trap 1: Your System Speaks a Different Language Than Your PBM
Most benefit administration platforms were designed for medical claims, premium billing, and eligibility files. They don’t natively ingest pharmacy rebate data. PBMs send rebate information in quarterly spreadsheets, PDFs, or flat-file extracts that no standard HRIS can automatically consume. So what happens in practice? The rebate check lands in your finance department. Someone manually applies it to the plan’s general fund. The link between that rebate and the specific prescriptions that generated it is broken forever. You never see which drugs drove the savings, which employees contributed most, or whether the PBM actually passed through the correct amount.
- The fix: Demand a structured, HIPAA-compliant data feed in your PBM contract: a delimited file or API export tied to claims and delivered on a set schedule. No standard EDI transaction carries manufacturer rebate data, so spell out the format, fields, and frequency. If your vendor can’t ingest it, ask why.
- The reality: Most mid-market employers accept PDFs and never realize how much they’re losing.
Trap 2: You Can’t Trace a Rebate Back to the Claims That Generated It
Pass-through means your plan receives the full rebate the manufacturer paid, drug by drug, instead of the PBM keeping a cut. To verify that, you have to trace each rebate back to the prescriptions that generated it. Almost no benefits system can do that. Why?
- Pharmacy claims data stays in the PBM’s system, not your HRIS.
- Rebate calculations are pooled across hundreds of drugs and thousands of members.
- Moving member-level pharmacy data into your benefits platform requires data-sharing agreements and safeguards that few employers have in place.
The result? Rebates get dumped into the plan’s general fund. That might look good on a trend report, but it hides which drugs and members generated the rebate dollars, so you can’t confirm the payment matches what your contract owed. Your employees don’t see the impact, and neither do you, at least not at the individual level.
Trap 3: Compliance Risks Hiding in the Data Gap
ERISA holds plan fiduciaries to a duty of prudence and requires plan assets to be used for the exclusive benefit of participants. Manufacturer rebates owed to the plan are money the fiduciary has to account for, and if you can’t produce a pre-rebate and post-rebate drug cost per member on demand, you can’t show that duty was met. HIPAA adds another layer: moving a rebate file with member-level NDC data into your benefits platform means that vendor needs a business associate agreement and the right safeguards. And the ACA connection is minimum value. Rebates don’t change what an employee pays for coverage, so they don’t move the affordability test. Minimum value measures the plan’s share of total costs, and if plan-retained rebates offset claims costs, they can affect that calculation. A plan that can’t track rebates as a separate line item can’t cleanly document whether it meets minimum value.
Three Systems Fixes That Actually Work
After working with employers who get pass-through right, I’ve seen what separates them from the pack. It’s not a better contract. It’s better system integration.
- 1. Require a machine-readable data feed in your PBM agreement. Not a quarterly PDF. Not a CSV you have to reformat. A structured, HIPAA-compliant file or API export with defined fields that your benefits administration platform can ingest automatically. Rebates don’t ride on standard enrollment or claims EDI transactions, so the format and frequency have to be written into the contract. PBMs can do this. They already do for their own internal analytics.
- 2. Build a rebate reconciliation module inside your HRIS or TPA system. Map the PBM’s rebate file to your enrollment and claims data using employee IDs. Create a monthly dashboard that shows total rebates, per-member attribution, and net drug cost. Most modern platforms have API capabilities or report builders that can handle this. If your vendor says they can’t, ask them to explain why, and then consider switching.
- 3. Audit the calculation and reconciliation, not just the contract. Hire a pharmacy auditor who specializes in systems validation. They should review how the PBM calculates rebate pools, how the rebate files are formatted and mapped, and how your benefits admin system processes that data downstream. Most leakage happens in the gap between two systems, not in the contract language.
CAA 2026 Makes Pass-Through a Legal Requirement
On February 3, 2026, Congress passed the Consolidated Appropriations Act, 2026. Among its PBM reforms, it requires PBMs serving ERISA group health plans to remit 100% of manufacturer rebates and related remuneration to the plan, with rebate aggregators and group purchasing organizations also required to pass funds along. Bona fide service fees are excluded. For calendar-year plans, most of these provisions take effect in 2029.
That moves the risk. A contract no longer has to win the pass-through argument; the statute now sets the floor. The law cannot move the money into a system that reconciles it. Under the new rules, PBMs are treated as covered service providers subject to ERISA compensation disclosure, and the Department of Labor has proposed rules to expand PBM fee disclosure. The question shifts from whether you negotiated 100% pass-through to whether you can verify what arrived. A legal right to a check you can’t reconcile is barely better than no right at all.
The Bottom Line
Rebate pass-through is not a contract problem. It’s a systems integration problem. A PBM can promise 100% pass-through all day long, and under the Consolidated Appropriations Act of 2026 it’s now a legal requirement for ERISA group health plans. But a statutory right to the money doesn’t fix your data pipeline. If your benefits administration platform cannot capture, reconcile, and report that pass-through against the claims that generated it, you’re operating on blind faith. The industry loves to talk about transparency. But real transparency requires systems that speak the same language. Until your enrollment platform, claims adjudicator, and PBM share a data pipeline for rebates, pass-through will remain a number you can’t verify, and your prescription drug trend will keep mysteriously outrunning inflation.
Ask your benefit administration vendor this week: “Where do you store pharmacy rebate data in our system?” If they pause, you have your answer.