We live with and care for my MIL who has multiple myeloma that has caused alarming dementia and loss of short term memory over the past two months to the point she has about 30 second retention at this point. We live in the suite in her two-level home to care for her. We cannot get her focussed to write any cheques to pay bills or do any bookkeeping, even with my husband's help, who is a (management accountant!) and we have spent into the thousands of dollars of our own money in the two months because of with no remuneration as we had to replace her dishwasher and purchase her a new mattress in addition to ordinary expenses that we have not been reimbursed for. There is an existing Enduring Power of Attorney that my husband and his brother are named on, which he is in possession of. I am wondering how we bring it into effect. She is still lucid and understands things, you just can't get her to attend to them nor does she remember 30 seconds after you have asked her to do it that you have asked her.
As POA your husband should be named on his mother's checking account if this hasn't already been done. Once that's done he can write and sign checks to pay his mom's bills (out of her money, not yours).
It's this type of situation your mom planned for when she named your husband POA. His POA kicked in the second his mom became unable to handle her own affairs.
You should carefully read the language of the POA. Some are very broad and give the designees some rights and access even before incompetence. Neither of my parents would be considered legally incompetent but they can not keep track of bills and accounts any longer. But I've been taking care of all financial matters using a broad POA for about 3 years now.
And make sure you compensate yourselves for any expenses for her home and care.
If you would like her Dr. to see the dementia make an appointment for your MIL to have a thorough physical. As POA your husband can call the Dr.'s office on his own and make sure that the physical will include a memory test. The memory test is very basic and is given while the physical exam is going on. It's almost like polite conversation from the Dr. and your MIL may not even realize she's being given a memory test.
It's never easy dealing with someone with dementia. As soon as we think we've got the person's dementia under control and know what we're dealing with, things change and we have to come up with a new strategy.