When setting up the loan request, enter a First payment date that is the appropriate month-end date. For example, if creating a loan request on August 25, you would specify that the first payment is due on September 30. Then enter a 31 into the Payment day field. This will trigger the system always to use the last day of any given month going forward (31, or 30, or 28 or 29 for February).
To adjust this on new loan requests going forward, set the Day of first payment as 31 using Tool #470 Loan Product Configuration using the Loan Product Defaults feature.
If you need to adjust dates for a batch of existing loans, contact a CSR for information about a custom flood project.