I want to delete ALL my data (accounts, balances, customers, etc…); how is this possible?

Welcome, @mme.

I see that you're planning to have a fresh start in QuickBooks Online (QBO). Let me help you then.

If your QuickBooks Online data is less than 60 days, you have the option to purge your account if you're using QuickBooks Online Plus, Essentials, and Advanced. The system deletes all data entered into the company, and you're unable to restore or reverse them.

Here's how to purge the data: 

1. Log in to your QuickBooks Online account.
2. Change the URL to include /purgecompany.
3. Example: URL shows https://...qbo.intuit.com/app/homepage, change to: https://...qbo.intuit.com/app/purgecompany.
4. The next screen will provide a summary of the items to be deleted.
5. Type the word “YES” once the data gets deleted, then click OK.
6. Click Wipe Data once your selections are complete.
7. Once the deletion is complete, you will be rerouted to your home page.

However, if our data is older than 60 days, we need to cancel our account and start a new subscription. Follow the steps on how to perform it:

1. Go to the Gear icon and select Account and Settings under Your Company.
2. Select the Billing and Subscription tab.
3. In the QuickBooks section, select Cancel.
4. Follow the steps to cancel your account. If you use payroll, you should cancel your payroll account too.

You can have this article for more information about the mentioned processes: Delete your data and start over in Quickbooks Online.

Never hesitate to come back here if you need additional assistance. I'll be happy to lend a hand. Keep safe, and have a good one.