HSA $1000 over age 55 prorated and how?

[RickD3]

My wife retired on 8/31/25. She had a family HSA plan of which I was a participant. We are both over 55. She contributed the max of $8,550 + $1000 (over 55 catch up). I contributed $1,000 to my HSA in January of 2025.

Upon her retirement, she retained a HDHP family plan under COBRA until the end of the year.

I applied for Medicare in August 2025 and Part A Hospital Medicare coverage began 2/1/25 while Part B Medical coverage began 9/1/25. I also retained coverage under her family HDHP until 12/31/25.

I assume her contribution for 2025 of $9,550 is fine but do I have to prorate my $1000 catch-up/over 55 HSA contribution made in January 2025? If so, do I prorate it from February or September? Also, if I have to prorate it, do I have to remove the earnings associated with the excess contribution or just the excess contribution?

I'm also guessing that she can make a full $4,400 + $1000 HSA contribution for 2026 assuming she retains her individual COBRA HDHP plan (she will not be Medicare eligible in 2026)

[NCperson]

@RickD3  once you are enrolled in Medicare, you are not eligble to make HSA contributions.  Since you signed up for Part A in Frbruary, you were only able to make a $1000 / 12  contribution for 2025. 

Your spouse on COBRA: yes, contributions are fine. 

[RickD3]

well, I signed up for Medicare in August, but Medicare Part A was backdated to coverage starting 2/1/25. Are you saying my $1000 catch-up contribution applicable to those over 55 has to be prorated such that I am only eligible for a $1,000/12 = $83.33 contribution and I must remove the difference ($916.67) from my HSA by 4/15/26?

[Mike9241]

It was backdated and went into effect on 2/1. it is not a HDHP.  Therefore, you had non-qualifying coverage starting 2/1

[NCperson]

@RickD3 yes