I would like to save all data prior to September 2018. Then once that data is saved, be able to wipe this data from Quickbooks Online. Can anyone help?

Thanks for visiting the Community, @info623. 

I can help you export your data to Excel before wiping them out from QuickBooks. Here's how: 

1. Go to the Settings icon. 
2. Select Export Data under Tools.
3. Click the Reports tab, then set the desired date range in the All dates drop-down list. 
4. Choose specific data you want to export by toggling the slider.
5. Click Export to Excel when ready.

Once done, continue exporting your data under the List tab. For more information, check out this help article: Export reports, lists, and more. 

To wipe out your data, you can follow the steps outlined in this help article: Delete your data and start over in QuickBooks Online. It will help you learn about when and how to delete your company data and start over. 

Don't hesitate to message us again if you have more questions. We're always delighted to help.