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Experience Period

The data used to calculate your experience modification is determined by your company's rating effective date (RED; prior to January 1, 2018, known as the anniversary rating date). The inception date, or start date, of your policies determines your company's RED. For example, if your policies always start on January 1, your RED would be January 1. If you have switched inception dates or if you have multiple concurrent policies with varying inception dates, determining your RED may be more complicated. Your insurance professional can help you determine your RED.

Your RED determines the experience period and the effective date of your experience modification. In most cases, all payroll and losses developed under any policy incepting or starting within the experience period are used in determining your experience modification. The experience period begins four years and nine months prior to your RED and terminates one year and nine months prior to the rating effective date. If your RED is January 1, 2023, the experience period is April 1, 2018 to April 1, 2021.

The rules concerning experience period rules can be found in the California Workers' Compensation Experience Rating Plan—1995

Experience Period table

2024  Experience Periods

The below table shows experience periods for rating effective dates throughout 2024.

Rating Date Inception Date Inception Date
01/01/24 04/01/19 04/01/22
02/01/24 05/01/19 05/01/22
03/01/24 06/01/19 06/01/22
04/01/24 07/01/19 07/01/22
05/01/24 08/01/19 08/01/22
06/01/24 09/01/19 09/01/22
07/01/24 10/01/19 10/01/22
08/01/24 11/01/19 11/01/22
09/01/24 12/01/19 12/01/22
10/01/24 01/01/20 01/01/23
11/01/24 02/01/20 02/01/23
12/01/24 03/01/20 03/01/23

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