California workers' comp

How to read a California workers' comp explanation of review (EOR)

Every reduction on a workers' comp bill arrives on an explanation of review. The EOR is where you find out what the carrier paid, why, and how long you have to object. Most practices post the payment and move on. Reading it line by line is how you find the money.

What every EOR must tell you

Labor Code 4603.3(a) sets the minimum. For every bill, the EOR must include:

1. The items or procedures billed and the amount you asked for.
2. The amount paid.
3. The basis for any adjustment, change or denial of each item.
4. For an incomplete bill, the additional information needed to decide it.
5. For a denial that isn't a fee dispute, the reason for the denial.
6. Whom to contact if a dispute arises over the payment.

It must also tell you the time limit to object and how to get Independent Bill Review. The DWC guide prescribes the wording: a section headed "TIME LIMITS TO DISPUTE PAYMENT AMOUNT" (Appendix B, Table 3.0). An EOR missing any of these is defective, and that's worth noting in your second review.

The reason codes that matter most

Paper EORs carry DWC Bill Adjustment Reason Codes. Electronic 835s carry the Claim Adjustment Reason Code (CARC) the DWC maps each one to. Four account for many of the reductions worth a second look:

Code text quoted from the DWC Medical Billing and Payment Guide, version 1.2.2, Appendix B, Table 1.0.

A worked example

An orthopedic office in Sacramento bills a knee injury: an established-patient visit, an injection and an X-ray on April 14, 2026, and an MRI on April 21. The EOR comes back like this:

The billed charge doesn't matter much. What matters is the gap between the OMFS maximum and what was paid, and whether the stated reason is true. Here the carrier was right about one line out of four. See how this bill gets appealed, step by step.

OMFS maximums are base maximum fees under 8 CCR 9789.12.2 for an office (place of service 11) in the Sacramento locality, from the CMS RVU26B file and the $51.6091 conversion factor adopted in 8 CCR 9789.19(m) (DWC OMFS), computed by Redress's fee schedule engine. The visit, bill and carrier responses are illustrative.

Check every line in five steps

1. Match lines. Line up each billed code and modifier with the EOR. A line missing from the EOR is an unanswered bill, not a denial.
2. Price the line. Look up the OMFS maximum for the code, modifiers, date of service, place of service and locality. That number, not your charge, is what the carrier owes for a correctly billed, payable service.
3. Read the reason. Translate the code (above) and note any remark codes.
4. Test the reason. Is the contract real? Was there an authorization? Do the modifiers and notes support separate payment? Was the paid amount actually the schedule amount?
5. Calendar the deadline. 90 days from service of the EOR. If it came by mail without proof of service, service is deemed five calendar days after the postmark (8 CCR 9792.5.5(b)).

PPO discounts: make them prove it

Network discounts are where many reductions hide, and California gives providers unusually strong tools. Labor Code 4609 requires the EOR to identify "the name of the network with which the payor has an agreement that entitles them to pay a preferred rate." If you ask in writing, the payor must "demonstrate that it is entitled to pay a contracted rate within 30 business days." If it can't, it owes the lesser of your fee or the fee schedule within 10 days of your written notice, and it can't take further discounts from you without your express written consent (LC 4609(c)).

When the EOR is late, or never comes

For a complete, properly documented bill, the carrier must pay at the fee schedule and explain any contested items within the deadlines above. If it doesn't, the uncontested amount is owed at the schedule "increased by 15 percent, together with interest at the same rate as judgments in civil actions" from the date the bill was received (LC 4603.2(b)(2)). The DWC guide calls the increase and interest "self-executing" (§6.4(b)): you bill for them and they're owed without a hearing.

What to do with a reduction that's wrong

Request a second bill review within 90 days of service of the EOR. If the only dispute is the amount and you miss that window, the bill "shall be deemed satisfied" (LC 4603.2(e)). If the second review doesn't fix it, you have 30 days to request Independent Bill Review, where providers win roughly nine times in ten. The appeal guide walks through both steps.

Last reviewed October 14, 2026. This guide is general information about California workers' compensation billing rules, not legal advice. Check the current statute and regulation before filing.