Can Domestic partner be made eligible for pre-tax deductions?

Summary: How do we implement scenario where domestic partners that qualify for pre-tax deductions ?

Content (please ensure you mask any confidential information): Client wants to implement option to have domestic partners that qualify/ provide certain documents to be eligible for pre-tax deductions, similar to spouse. Please advise on how this can be accomplished and if this has been implemented in other organizations. The expected population of Domestic Partners that would qualify would be around 30-40.

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