My mother is applying for chronic Medicaid. She is 96 and needs nursing home care. Is her son's joint account her asset?

Whomevers Social Security # or #’s attached to the account is / are the “owner” of the account.

Ask bank as to exactly whose name & # it is?
hopefully it’s just his and mom is only a signatory on the account. The bank will have the paperwork on this. Your brother will have to get the bank to do this.
but if not then it’s a shared account, then between your brother & her (or you as DPOA) will likely have to go thru banking history to establish that none of the $ is hers.

Right now, where is her SS monthly income going?
That’s going to be very important as that account & it’s balance will need to be furnished to the state for her LTC NH Medicaid application. How many months really seems to depend on how your state administers Medicaid. Some want 5 years, others 3 years, others less.
if moms SS$ is going into bro’s account, it’s viewed as a commingled account and that usually means the $ in it is accessible to either and completely. Medicaid could view it all as hers.

whatever the case it imo has to, has to, get mom removed from it. If Bro should predecease mom, all the $ in the acct becomes hers. And it will make her ineligible for Medicaid. If he’s not competent to do his financials or manage his affairs, then he likely needs a guardian or conservator & needs to get accounts POD (pay on death) to the guardian, you or whomever will be the eventual executor of his Estate as per his will.

SS has rules on commingled accounts.... it’s very much frowned upon & if found out SSA can require mom to become his representative payee. Which I’m guessing mom really isn’t in a position To do at all since she’s at 96 & needing a NH. VA also has rules on this if his income is coming from VA.

you have a lot of interlocking parts in your families situation. Between you bro’s disabled vet status and mom’s commingled account situation, it’s gonna get complicated. Really it would be worthwhile to have bro to use the $ her has to pay for a disability rights attorney who has an Associate who does elder law & they both turn review the situation and shepherd moms LTC NH Medicaid application and figure out some sort of Trust and guardianship for your brother. It’s not a DIY imo. Your family needs an atty who understands just how NY state runs its programs.

Look back is exactly that, where did these funds come from, does he have proof as to when he added her name? How much was in the account at that time? Did she add any funds?

If I have read what you have said correctly, this account was in his name only and he added her, if so, and with proper documentation it should be ok, might take some explaining and proof tho.

It's a shame that the veteran son wasn't advised to give his mother - or indeed somebody younger and in better health - power of attorney to handle his money for him rather than adding his mother to his bank account; but I shouldn't have thought that Medicaid would now regard *his* funds as belonging to his mother even though she had access to them for specific purposes.

But ring and ask their advice, I should.