From the Hotline: Discrimination and Marriage Documentation Requirements
Question: Is it discriminatory if an employer requires a domestic partner affidavit for same sex marriages but does not require marriage certificates for opposite sex married employees?
Answer: The best practice would be consistency in the application of your employee policies relating to documentation requirements so as not to create the appearance of different treatment for different groups of employees.
In general, if employers are not asking for proof of relationship for other dependents for benefits purposes and there is no carrier requirements to do so, then the employer should not be asking this of “domestic partners”. An alternate general practice that allows for “loose” interpretation is to have all employees assert via signed affidavit that dependents they are enrolling meet the definitions as set forth in the insurance plan. Then the employer can define dependents more specifically including domestic partners. This practice can mitigate claims of unlawful discrimination based on local, state, or federal law.
Contact your benefit plan administrators or benefits counsel to ensure that benefits are being administered in accordance with the plan requirements as well as to ensure consistency with applicable state and federal laws relating to same-sex spouses and registered domestic partners.