The U.S. Department of Labor finalized a sweeping PBM disclosure rule requiring pharmacy benefit managers to share extensive compensation data with self-insured employer clients. Regulators expect the rule to reduce drug costs for employers and workers by $22 billion over a decade. The final rule, effective July 2027, compels PBMs to disclose detailed payment flows including rebate arrangements and “spread” payments, delivered when negotiating or renewing employer contracts and again every six months. Employers will be able to audit the information annually, with noncompliance carrying financial penalties and possible contract invalidation. PBMs and their trade groups have opposed the rule, arguing it undermines business models, while employers and policymakers have backed it as a way to pierce opaque fee structures that have long complicated negotiations over formulary and pricing. Separately, industry commentary tied the final rule to a broader push for transparency across the drug supply chain, where employers see limited ability to validate stewardship without contractual visibility into PBM economics.