What Is California Labor Code §4603.3: Explanation of Review Notice?

Upon payment, adjustment, or denial of a complete or incomplete itemization of medical services, an employer shall provide an explanation of review in the manner prescribed by the administrative director that shall include all of the following:

What does Labor Code 4603.3 require, in plain words?

It requires a clear, written notice every time a medical bill is paid, changed, or denied.

A California workers' comp claim involves many medical bills. Your doctor, a hospital, or another provider sends a bill to the claims administrator. Labor Code 4603.3 requires a response called an explanation of review, often shortened to EOR. The claims administrator sends the EOR to the provider, not to you. This applies whether the bill is paid in full, paid in part, or denied.

What must the explanation of review say?

The law lists six things the notice must cover.

Labor Code 4603.3 requires this notice to include each item below.

That last item points to independent bill review under Labor Code 4603.6. A provider uses that process only after a second review does not resolve a dispute over the amount paid.

Why does this notice matter to you if it goes to your doctor, not to you?

A clear, timely explanation of review helps keep your medical care on track.

This notice is addressed to your medical provider. It still matters to your claim. A provider who gets a clear, timely notice knows what was paid and why. A provider who does not may delay further care, or ask you about the bill directly. Once you file a claim form, Labor Code 3751 generally bars a provider from billing you directly for the injury, unless your employer has rejected the claim in writing. This step helps keep billing disputes between the provider and the claims administrator, not you.

What happens if the claims administrator pays late or skips the notice?

A late or incomplete explanation of review can trigger a payment increase and interest.

Under Labor Code 4603.2, payment is due within 45 days of the bill, along with the explanation of review. A bill that is not properly paid or contested within that window can be increased by 15 percent, plus interest. If the provider disagrees with that notice, the provider can ask for a second review within 90 days. An unresolved dispute after that goes to independent bill review under Labor Code 4603.6.

How does this notice connect to medical-legal bills and the rest of your claim?

The same notice requirement also governs medical-legal bills, with their own payment deadline and penalty.

Labor Code 4622 uses this same explanation of review to dispute a medical-legal bill, which pays for an evaluation or report used to decide your claim. Labor Code 4621 covers which medical-legal expenses get reimbursed in the first place. Labor Code 4603.2 covers the broader payment and review process for ordinary treatment bills. Each of these rules relies on that same notice to start the clock on a dispute.

If a billing dispute is slowing down your medical care, or you are not sure what a notice about your claim means, a short call can help. Yazdchi Law P.C. reviews each matter individually. For the bigger picture of how a claim moves from injury to payment, see the firm's guide to the California workers' comp claim process. Call (661) 273-1780 or use the contact form for a free consultation.