Whenever a new month occur you need a specific activity to happen, "Do The Monthly Work".
Initially you need to start the process. This is done by executing "A: Start process". This could be done automatically by a Robot user. Once we can set initial delay and deadlines on activities (expected in the summer of 2021 in release 6.5) we can avoid this activity.
The Robot executes the "B" activity once monthly on the 1st of the next month.