You can purge your data if your account aged is less than 60 days. Please keep in mind that this process only works for QuickBooks Online Plus and Essentials. The system deletes all data entered into the company, and you're unable to restore or reverse them.
To purge the data, follow the steps listed below:
Log in to your QuickBooks Online account. Change the URL to include /purgecompany. Example: URL shows https://qbo.intuit.com/c28/app/homepage, change to: https://qbo.intuit.com/c28/app/purgecompany. The next screen will provide a summary of the items to be deleted. Type the word “YES” once the data gets deleted, then click OK. Click Wipe Data once your selections are complete. Once the deletion is complete, you will be rerouted to your home page.
If not, you need to cancel your account, and start a new subscription.
QBO is not allowed to delete any List data but only hide it. I would recommend to open a new QBO account and migrate your data by using a 3rd party migration tool.