Will the HSA transfer to me when my husband turns 65? I doubt it. Since each taxpayer must have their own account. Talk to the employer so things don't get messed up.
Your husband cannot make a family contribution for December because of his medicare coverage.
assuming a family plan can make a maximum family coverage contribution of (8300+ 1000 over 55 catch up) times 11/12= 8525
if you open your own HSA for December you can contribute
4150/12 + 1000 =1346 your contribution
