Mom's cognitive skills are diminishing and she won't let me help pay bills. What can I do about bills that are late or unpaid?

Another alternative is to pay the bills through online banking, do you have POA and are you able to set this up with your mom's bank?

I was on all Moms utilities and other bills as the person to contact if payments weren't made.

My Mom asked me to pay her bills. It started out that we did it together. I wrote them, she signed them. Eventually, I did it all and signed with POA behind my name. I also was on her account.

Autopay is the way to go with dementia or not. I haven't paid a bill in over 10 years. It just happens.

I live in Texas and found that I was only asked for a POA by the credit card company when I wanted to cancel the card after my Mother died. Before that I simply called the utilities and explained the situation telling them I was trying to make sure Mom's bill got paid. EVERY one of them willingly changed the mailing address to mine. I was a signer on her checking account and paid them by check. Pretty much, all they were concerned with was someone paying the bill.

Agree, set up automatic bill paying. I remember when my BIL had both his mother and his aunt, different residences, both with early dementia. And working and supporting his own family. He set their bills up on autopay, and slightly overpaid the utility bills that fluctuate. When he visited, he reviewed the utility bills and adjusted those payments. That way he handled their bills approximately quarterly, only utility bill adjustments. They both eventually needed AL, and finally NH. In my opion he was a saint.

I agree with autopay.  Also, if you don't have it already - get POA.  Very important, before she declines any more.

Agree with auto pay. Explain in detail why it's a great idea. Mother stopped paying her bills about ten years ago. She wasn't even opening her mail. I set up all her utilities and insurances on draft.
Of course her first reaction was, "Oh, no no no." So, I explained to her how it would work and how it could be a matter of emergency if her phone was disconnected and she couldn't call out, how she could still get a paper bill showing what was drafted, etc. Then she was in agreement and we went to the utilities and arranged it. At that time she was just beginning to show signs of dementia .

Ive had auto pay for my insurance and long term bills for years and am beginning to consider for my phone too tho i just like having the ability to see the charges for it.

By having auto pay i know if i get sick i dont miss a bill and lose coverage.

Auto pay . Also, our utilities have a third party notification where a bill can be sent to a designated person in addition to the account holder to be sure it gets paid -or hasn't been lost in the mail, etc. You could put her checking account "on-line" and set up bill pay - most bills come about the same time each month - go online to them get amount and pay from her account. (That way you'll know if she has already paid bill.)

Unfortunately, when we tried to help my mother who was diagnosed with Alzheimer’s when she started not paying her bills, she was terribly resistant, even stopped speaking to my brothers and I, and threatened to sue us. We had to enlist an attorney and, go to court and do a “benevolent take over” of all her affairs. We did have to present medical proof of her dementia to the courts,
As her daughter, I became court appointment guardian, POA and trustee. With the court documents it was easy to change her accounts, take control of all her assets, even medical decisions. Taking things to court is costly and time consuming. But, full proof and necessary if the person is deteriorating and resistant.