Is it legal (California, USA) for an employer to require an employee provide a copy of the first two pages of their most recent form 1040 as part of demonstrating the eligibility of the dependents for medical, dental, vision, etc. insurance benefits?
This demand is being made in addition to a copy of the marriage certificate as well as birth certificates for dependent child(ren).
Specifically, they are demanding:
the first page (both sides) of your most recent federal income tax return Form 1040 (either one joint return or the returns of both parties, if you are filing separately) showing filing status, the signatures and date signed of the employee and spouse (blacking out the financial information).
Additional (presumably equivalent) instructions are provided for those filing electronically. The requirement is waived for those who have been married for less than one year.