Last week, daisyNews documented how Employers Compensation Insurance Company denied bills by questionably citing MPN non-membership, and how providers have no real recourse. Today, we spotlight something that dramatically demonstrates the utter ineptitude of the California Division of Workers’ Compensation (CA DWC) in overseeing the MPN system.

As this series has pointed out, it can be extremely difficult, or even impossible, for a provider to determine when an MPN applies or to confirm (or prove) their own membership therein. In large part, this is due to the CA DWC’s failure to maintain a functioning, up-to-date, public MPN database.

The state’s broken MPN database arguably enables the practice of incorrectly denying payment for alleged MPN non-membership.

The CA DWC’s online MPN list includes 2,533 entries, the vast majority of which are listed as “W” (Withdrawn), “T” (Terminated), “S” (Suspended), or otherwise out of commission. The page allows visitors to view a filtered version of the list that displays only “Active” MPNs…but that view lists only a single MPN with a status of “L.”

According to the CA DWC, “L” refers to “Limited liability.” Providers are instructed to contact the CA DWC Medical Unit to verify the MPN’s actual status.

Of course, there are hundreds of active MPNs. But for whatever reason, the CA DWC couldn’t separate them from the list of thousands of defunct entities on the searchable list.

This is the official state list from which providers should be able to get accurate information. Payers and other nebulous “entities” that maintain MPNs do not reliably make provider rosters or other information available. The state website is the last backstop for providers and injured workers seeking to determine who can provide treatment.

For the CA DWC to allow this glitch (and others) represents all that providers need to know about the MPN system’s impact on ensuring injured workers’ access to care.

"Showing 1 to 1 of 1 entries"

The CA DWC's MPN landing page presents the state’s list of MPNs under three tabs:

• MPN List Approved By Date
• MPN List Approved By Name
• Active List of Approved MPNs

Reasonable people, including providers trying to determine MPN applicability or membership, injured workers looking for an eligible physician, or an employer verifying its insurer's network, would click the "Active List of Approved MPNs" tab expecting to see a list of active MPNs that are actually operating in California.

What they find is a single MPN, the BBSI MPN (MPN ID number 409):

The BBSI MPN, approved in 2005, has an MPN Approval Status of L.

The page does not specify what  L refers to. There is no key or legend on the page. To learn what L means, providers have to download the CA DWC's PDF version of the active MPN list. On that list, the BBSI MPN has an asterisk. A key at the bottom of each page notes:

“* = Limited liability, contact DWC Medical Unit to verify.”

CA’s MPN Morass

A provider, injured worker, employer, or regulator trying to use the state's official MPN source has two options: manually wade through 2,533 entries or call the employer or insurer.

For a taste of just how difficult it can be to confirm MPN applicability and provider membership, consider Marriott. The hotel chain’s MPN is listed under a vendor’s name, while the MPN website is on a different company’s URL. The provider roster is secured behind password protection, on a page with fine print stating that the vendor "does not warrant the accuracy of the information or the quality of medical care."

The entire point of the CA DWC MPN list is to provide the state with an authoritative, accessible source of accurate information that can otherwise be extremely difficult to find, as in the Marriott example. As a tool to help stakeholders, it fails miserably.

Moreover, this is not the MPN page’s first major glitch.

As daisyNews has documented, four of the last six times the CA DWC attempted a quarterly update to the MPN list, the list vanished entirely, sometimes for weeks. This happened in July 2024, October 2024, January 2025, and October 2025.

MPN Mess Creates Payment Denial Opportunities

The CA DWC's failure to maintain an operable MPN database allows claims administrators to incorrectly deny providers’ reimbursement for treating injured workers by simply claiming some version of “provider not in network” as the denial reason.

From January 1, 2025 through April 30, 2026, six major California workers' comp payers in daisyBill’s system collectively denied 43,458 bills on those grounds. As we noted last week, the rates at which some payers cited MPN non-membership as their denial reasoning strain plausibility: Employers at 60%, QBE at 44%, and Sedgwick at 29%.

With multiple examples where the provider in question was in the payer’s MPN, is the rate of these “errors” plausible?

Theoretically, any payer seeking to increase profits by playing the MPN payment denial card regardless of the provider’s actual MPN status couldn’t ask for a more favorable environment:

• Explanations of Review don’t have to specify the injured workers’ MPN when non-membership is the payment denial reason.
• The CA DWC’s list is a farce, leaving providers without a reliable way to confirm MPN applicability or membership therein.
• One of the only ways to dispute a denial is to take a screenshot of the provider roster from the MPN website (which may be difficult to find or not exist at all) and file a Second Review appeal with the payer that issued the denial. According to the CA DWC, IBR is not an option.

CA DWC’s Failure = Employer’s Cost Burden

The downstream cost of MPN dysfunction falls on California employers and their injured workers. Specialists opt out of workers' comp rather than fight for reimbursement for authorized, in-network services. As a result, injured workers can't find doctors.

Every day of delay is a day the employer potentially pays disability benefits (up to $1,764 per week in Temporary Total Disability alone).

Payers receive billions in premiums to operate inside this broken system. The administrative friction that MPNs and other counterproductive complications drive raises claim costs. That in turn fuels the argument to raise premiums. In California, those premiums went up 8.7% in 2025, with another 10.4% hike proposed for 2026.

The CA DWC's MPN apparatus is not failing because the problem is particularly difficult. It is failing because no one with the authority to fix it has chosen to. Meanwhile, the beneficiaries of this profitable dysfunction continue to reap the profits.

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