My sister and I are taking over our parents finances. How do we approach our very stubborn, but demented Dad to get access to all their info?

I agree with a poster above. Don't put your names as a primary on any of your dad's accounts. However, you and/or your sister can be secondary on his accounts.

You have several options since you have POA. When you go to the bank just find out what your options are and which is most suited to your situation.

It might be wise to have a face to face chat with that non-relative who has appeared. Never hurts to let a questionable party know they are being observed.

GardenArtist -- I agree with your advice, only if the parent has shown a lifelong pattern of being reasonable, flexible, and cooperative. Many children are given the responsibility of being attorney-in-fact, but the parent did not give them their trust and confidence as well. Don't ask me how I know this! Lol...
If the parent is known to be unreasonable, overly controlling, rigid, and oppositional - then the children are in the very uncomfortable postition of having to take charge without the parent's consent. It's necessary that they do this, if they've accepted the role of attorney-in-fact.

It's tough but can be done. Once you have all the paperwork in order, you should be able to take it to the bank and get accounts changed to your names and whatever mailing address you wish and the same with utility companies and credit cards. If you have a lawyer that Dad is comfortable with perhaps he can come meet with everyone and explain why this is necessary. Sometimes elderly listen better to an outsider than their own flesh and blood! Good luck.

I would assure Dad that you will keep him informed of all financial dealings and go over bank account each month. It is still his money and perhaps this will make him more comfortable.

Do not change bank accounts to your names. You file the POA with the bank and, in that way, gain access to the funds. If you actually put the accounts in your names, they become YOUR assets and subject to lawsuit recovery, divorce settlement, etc. Leave ownership in their names. That best protects their assets.

What I'd probably do (if dad really IS incompetent) is to get them out of the house and then find all the paperwork myself, confiscate it and take over the responsibilities. I'd let him know what I was doing after the fact and just accept that he was going to be angry.

I'd discuss every single check I wrote with him and give him a monthly statement of his accounts as long as he was interested. After a while, as his dementia progresses, he won't care anymore.

I'd only do this if I REALLY BELIEVED he was incompetent, though. It's the nuclear option.

I would offer a slightly different approach. If your father is "aware" despite dementia, why not try to work with him to ASSIST him rather than just taking over?

This isn't intended to be critical, but I read your post several times and couldn't help get the impression that this is somewhat of a power grab, that you and your sister are determined to take this action one way or the other.

You don't indicate if there are factual justifications, or what your mother's status is.

Have you tried a "Mom and Dad, we'd like to help you approach first?"

That approach may not work, but your parents are entitled to know what you're doing. They apparently trusted you enough to name you as their attorney-in-fact, so you need to show that you're worthy of it.

And unless there are facts that haven't been stated, I really do think that going their documentation while they're not home is very offensive and invasive.

Try to think of a less confrontational method of handling this and show that you are capable of handling their affairs on a professional basis.

Looloo, I understand your point. Thanks for sharing!

Thanks Garden/Artist - since we are new at this, all advice is gratefully accepted. After some thinking and talking we are slowing down and will take it in baby steps. I think first we will just help with bill paying. The POA gives us access to their accounts so we can just watch and keep an eye on things. We don't need to rush in there and take stuff without their knowledge. We will sit down and have a talk. My dad's dementia has made him aggressive, paranoid, and unreasonable. He does not trust us, unfortunately, so we know this change will make him very upset. He does not think anything is wrong with him. Our mom has Alzheimers and is pretty passive and actually would love the help with the bills They have been having trouble paying bills, losing things, late fees - donating large amounts to questionable charities. Now a distant non-blood relative has showed up and we are worried they will start giving her money. The doctor and our social worker have said that they are close to needing assisted living and are concerned and willing to write an incompetence letter to the lawyer. So we are going to go ahead and do this even if my dad is not cooperative, because we need to help and protect our folks. Thanks for all the advice, this is so hard!

It sounds like you and your sister are a united front, so that's wonderful! If you both live near your father and visit him together, then one of you could try distracting your father, or taking him out of the house for a while. Then one of you could go through the files at home. I took a few statements and invoices from each file -- they didn't have to be the most recent. You can build your own files from these.
Also, it's helpful to get copies of all his credit cards and i.d. -- whatever he carries in his wallet. Some institutions ask for a copy of a photo i.d. And having all of his credit card info is very helpful (get the security code on the back too).
If he drives, get his car registration info as well. And copy down all the info on his prescriptions as well. Begin communicating with his doctors if you haven't done this yet.
That ought to make a dent in things :) Last, now is the perfect time for you and your sister to get comfortable with taking over things. It feels very disrespectful and sneaky in the beginning, but it's necessary, and the sooner you get used to being in charge of these things, the better. Good luck!