I wanted to also add that mandatory HSA contributions could be administratively problematic for the employer since there's a dollar limit on the HSA contributions. Personal example: as part of my benefits package, my employer contributes up to the HSA limit for family coverage. My spouse who is not covered by my employer, but his own employer's coverage, signed up for an HSA and "unknowingly" received a minimal contribution to his HSA account (-he didn't bother to read the fine print). It was a pain trying to correct the overage.