Both I & my wife have separate HDHP plan. My kids are on my plan & I contribute family max 6900 to HSA. Can my wife also contribute 3400 to her HSA We file Joint return

[BMcCalpin]

Unfortunately, no.

The IRS requires that if either spouse is under Family HDHP coverage, then both spouses must report Family coverage.

What this means is that the two spouses must share the Family contribution limit of $6,900. That is, the aggregate of all HSA contributions to either HSA must be no more than $6,900 if you are both under 55.

So, one spouse can't max out the Family limit while the other spouse maxes out the Self-only limit.

Sadly, this is not well-understood, and many people end up making excess contributions each year by not realizing this. I am glad you asked first.