For the Statements Provided by Your Lender averaging method, Pub 936 provides the following guidance: 'If you receive monthly statements showing the closing balance or the average balance for the month, you can use either to figure your average balance for the year.' Your interpretation of this is at least as good as mine but remember, Pub 936 only provides guidance on applying the tax regulations.
You can pick the consecutive 12 month ending balances based on the balance after the monthly payment is maid. I'm guessing that the ending balance on your December 04, 2024 statement shows the balance after applying the payment due Dec 1 ($444K) and that payments are made on the 1st of each month. This is the amount you would use for Dec and then be consistent with the preceding 11 months.
Another way to approach this is simply use the balance on the last day of the each month, whatever makes sense to you. You don't have to use the same day on all three loans but be consistent month-to-month on each loan individually.
