In California, Medical Provider Networks (MPNs) theoretically allow employers and their comp insurers to ensure that injured workers receive appropriate care at reasonable costs. We argue that, in practice, MPNs function primarily to bully doctors into discount reimbursement contracts and to justify (accurately or not) payment denials based on non-membership in MPNs.

We've seen multiple examples of payers denying reimbursement by citing non-membership in MPNs where:

• The MPN is unspecified, inactive, or nonexistent
• The provider is a member of the applicable MPN

In other words, MPN-based payment denials can be, and often are, invalid.

daisyData reveal that some payers deny reimbursement by citing MPN non-membership at significantly higher rates than others. For example, our data show that 60% of payment denials from Employers Compensation Insurance Company cited “Services not provided by network/primary care providers.”

That implausible statistic raised enough suspicion for our team to investigate. We discovered multiple examples of MPN-based denials from Employers in which the provider is an active member of the only active MPN the state lists for that insurer.

This is a consequence of an MPN system that the California Division of Workers' Compensation (CA DWC) only nominally manages, with thousands of (mostly defunct) MPNs in play, often with no discernible connection to the employer or insurer, each of which can add or remove providers seemingly at will, and no public information specifying the criteria for MPN membership.

As we regularly point out, it is often impossible for doctors to determine whether an MPN applies to a given injury or whether the provider is a member of the applicable MPN. That confusion is bound to create the conditions for abuse, which our data strongly suggest is occurring, possibly at scale.

Below are the data from the 10 payers in our system that most frequently cite MPNs to justify payment denials. Providers, pay attention to your Explanations of Review (EORs), and never assume that an MPN-based denial is legitimate.

Data: MPN Denials January 1, 2025 – April 30, 2026

The table below lists the ten insurers and Third-Party Administrators (TPAs) that most frequently cited MPN non-membership as justification for payment denial for e-bills sent from January 1, 2025 through April 30 of this year. For each payer, we list:

• The total number of bills daisyBill providers submitted
• The total number of daisyBill providers' bills the payer denied
• The total number of denials that specifically cited MPN non-membership
• The percentage of denials that cited MPN non-membership

Most significantly, Employers denied 7,339 bills for MPN non-membership, an astonishing (and deeply questionable) 60% of the 12,155 bills that Employers denied in total.

QBE North American came in second, denying 44% of bills for MPN reasons. Sedgwick Claims Management Services, Inc., the largest TPA in our system (and the nation), denied 26,947 bills for MPN reasons, representing 29% of its total denials.

Employers Compensation Insurance Company: A Closer Look

Given Employers' statistics, we decided to spot-check several of the bills Employers denied and investigate the MPN status of the provider in question.

On January 7, 2026, Employers denied payment to a Ventura County provider, citing Claims Adjustment Reason Code (CARC) 242: "Services not provided by network/primary care providers."

On its not entirely reliable online list, the CA DWC lists only one active MPN where Employers is the MPN applicant: Employers MPN, with MPN ID number 37. When we went to the website that the CA DWC lists for Employers MPN and searched the provider roster, the provider was listed as a member.

The above was only one example.

On February 2, 2026, Employers denied payment to a Kern County provider, citing CARC 242: "Services not provided by network/primary care providers." We checked the Employers MPN provider roster, and sure enough, the provider is listed as a member.

The same scenario played out for a March 19, 2026 date of service for a Solano County provider that Employers denied with good ol' CARC 242.

Providers, especially those billing Employers, must monitor their EORs and watch for these questionable denials. If you can determine that you are an MPN member, appeal accordingly (more on that in tomorrow’s article).

Providers quite literally pay to be members of these MPNs by sacrificing revenue to Preferred Provider Organization (PPO) discounts that multiple payers, bill review services, and other assorted middlepeople have access to. The least that payers can do is reimburse at the contractually reduced rates.

Never assume that an MPN-based denial is legitimate.

Documented instances of invalid MPN-based payment denials should result in consequences. But in California, it does not. In future articles, daisyNews examines how Employers (and every other payer committing these violations) gets away with it.

daisyBill lets you submit appeals against bogus denials in seconds. Schedule a quick chat to learn how we get doctors paid faster and more accurately.

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