@W16VA
If you are not currently enrolled in Medicare, you can contribute to an HSA (provided you are enrolled in an eligible HDHP and have no "other" medical coverage. However, be aware that when you do enroll in medicare, your enrollment will be backdated 6 months. That means, for example, that if you tell medicare you want to enroll on Jan 1 2026, it will actually be official July 1, 2025, and that will limit your 2025 contributions. So you need to keep that in mind.
If your spouse is age 55 or older, she gets a $1000 catchup contribution, that can only be contributed to her HSA. You also get a $1000 catch-up contribution that can only be contributed to your account. The general family limit ($8750 for 2026) can be split between you any way you like, but you can't exceed $8750 in total. That means, for example, that you could each contribute $4375 plus $1000. Or, you could contribute $8750 plus $1000 and your wife could contribute $1000. Or any other combination that makes the math work.
This also affects your contribution limits when you enroll in Medicare. Suppose you work and maintain your family HDHP coverage until December 31, 2026. Your Medicare would be retroactive to July 1, 2026. That means that for 2026, your contribution maximum would be half (6/12ths) of the family limit plus 6/12th of the $1000 catch-up. But your wife's contribution limit is unaffected by you going on Medicare as long as she is still covered by your family HDHP. So she could contribute the family maximum in 2026 even though you cannot (subject to the same rule that you can't exceed the overall total. In other words, your limit for 2026 would be $4375 plus $500, but her limit would still be $8750 plus $1000, as long as your two family limits did not exceed $8750. Also, you can make the contributions any time during the year, even after you enroll in Medicare, as long as the total for the year does not exceed the allowable total. What matters is the yearly total, not when in the year the contribution is made.
You save more taxes if you contribute via payroll deduction, because payroll contributions are also excluded from Medicare and social security tax. That means that, in the 22% tax bracket, your wife's contributions would result in a 22% deduction, but if you can make workplace contributions, you will save 29%.
I believe that your employer would not be allowed to contribute to your wife's HSA, regardless of whether you have one or not. I could be wrong, you may want to ask them to clarify. So you would contribute to your HSA from payroll deduction and your wife would contribute by sending a check or making an electronic payment from any convenient bank account you might have.
The most tax-efficient strategy is to contribute as much as you can afford via payroll deduction (up to $9750 for 2026), and then contribute the extra $1000 from other out of pocket funds to your wife's account. As I said before, she will probably have to open a private account rather than using the payroll plan that your employer offers. Then, when you get close to going on Medicare, you can adjust your contributions for that year to maximize your use of the family limit by putting more into her account and less into yours, since your contributions will be limited by your Medicare enrollment.
