My 94-year old mom lives with her 75-year old brother. They have a joint checking account which is her funds. As her POA, can I write checks on their joint account?

Aloha, it is better if Mom has her own account with you listed as a co-signer. Mom would still be the main account holder with her bank "interest" connected to the IRS. Have all of Mom's bills and statement forwarded to your home. That way bills/statements won't get lost. My Dad thought those items were junk mail and threw them away... oops.

I bet Mom's brother will be relieved that he doesn't need to bother with his sister's bills. By the way, who is your Uncle's Power of Attorney? Whomever it is, time for him/her to step up and help the Uncle with writing checks for his bills.

You cannot write checks unless you are a signator on her bank account. Approach the bank to make arrangements, but be sure that you know your legal responsibilities as a POA.