Solution:
Schedule the first Bill Run to execute on the last day of the months which have 31 days, i.e. 31st of January, March, May, July, August, October or December and select to repeat monthly. The subsequent Bill Runs will trigger on the last day of each month. E.g. Feb 28th (or Feb 29th in the leap year), March 31st, April 30th, May 31st, June 30th, etc.
