Can a California employer ask what you currently earn?

The rule exists because asking the question carries pay gaps forward. If an offer is anchored to what somebody was paid before, an underpayment made years ago by a different employer follows the person for the rest of their career, and does so most often to the people it was already following.

The prohibition is broader than the interview. An employer may not seek salary-history information about an applicant, and may not do so through a recruiter or a background-check vendor either — using an agent does not change the answer. Nor may prior compensation be relied on, by itself, to justify a pay difference.

There is a narrow exception that gets over-read: if an applicant voluntarily and without prompting discloses what they earned, the employer may consider it. "Voluntarily and without prompting" is doing real work in that sentence. A form field, a screening question, or a recruiter who asks conversationally is none of those things.

The reciprocal duty is the part small employers miss. On reasonable request from an applicant, the employer must provide the pay scale for the position being applied for. Refusing is its own violation, and the request is usually made in writing by somebody who already knows the answer.