I sold my condo on August 29th and double checked at closing that I didn't need to pay the September mortgage payment. Which meant I hadn't had to pay both mortgages at once, because the mortgage for the new house had its first payment out Sept 1.
And September 2 I discovered that I had not canceled the auto payment like I thought I had. 🤦♀️
They did refund me in full (and I got a second check in the same amount which I wonder if it was a clerical error but I'm not questioning it), it just took a few weeks.
You shouldn't have that issue with rent but man I felt so dumb 😄