“For federal tax purposes, marriages of couples of the same sex are treated the same as marriages of couples of the opposite sex. The term "spouse" includes an individual married to a person of the same sex. However, individuals who have entered into a registered domestic partnership, civil union, or other similar relationship that isn't considered a marriage under state law aren't considered married for federal tax purposes.” –IRS Publication 969
With the Supreme Court ruling on DOMA on June 26, 2013, same sex marriages are now recognized by the Federal government, and therefore the HSA rules that apply to married spouses filing taxes together apply to same-sex marriages. Individuals in a same sex marriage share the family HSA contribution limit and can use HSA funds on each other if they are in the same tax family. If either spouse has family HDHP coverage, both spouses are treated as having family HDHP coverage. If each spouse has family coverage under a separate plan, the contribution limit for 2017 is $6,750. The contribution limit is split equally between the spouses unless you agree on a different division. These rules for married people apply only if both spouses are eligible individuals. If a spouse is 55 or older and not enrolled in Medicare, that spouse's contribution limit is increased by the additional $1,000 catch-up contribution. If both spouses meet the age requirement, the total contributions under family coverage cannot be more than $8,750. Each spouse must make the additional contribution to his or her own HSA.
Click here to read the Internal Revenue Bulletin: 2014-2 from January 6, 2014, Notice 2014-1, Sections 125 and 223 – Cafeteria Plans, Flexible Spending Arrangements, and Health Savings Accounts — Elections and Reimbursements for Same-Sex Spouses Following the WindsorSupreme Court Decision