Sometimes you just want to start fresh. Informant Sync data sits on a server so to start fresh you need to erase your local data and also the data that is on the server.
To erase the data on the server, open the Informant Sync account settings and then choose Reset Informant Sync Account at the bottom:
This process will run on the server, but will return immediately. Please wait about 10-15 minutes for small accounts and a couple hours for large accounts. You can check if the data has been erased by using the Data Statistics button on the same page.