How do I keep track of expenses for Mom and Dad such as transportation, care services?

Thanks for your help.

Try to keep track of all expenses. If your parents pay you to be their caregiver here is a sample form https://www.agingcare.com/documents/personal_care_agreement_AgingCare.pdf.

What I am doing with my Dad, since he always depended on my Mom to do all the bill paying and she has since passed, I am gathering up all his bills and paying them out of my own checking account. To keep a record I make a copy of the bill and check together on one sheet of paper and file it. Then I keep a running tab on what I have been paying, then my Dad will reimburse me. That way if for some reason he needs Medicaid, it will prove that checks written to me were for bills, not money given away to me.

Or see if you could become a signer on your parent's checking account, so that you can pay bills for them from their own accounts.