If you have used QB account for more than 60 days, and now you want to delete specific customer and restart it in QBO, then you need to follow the below-given steps:

First, Discard your Current Account
For this, click on the Settings option and then go to the Account and Settings button.
Then, navigate to the Billing and subscription tab and hit Cancel subscription.
Now, follow the on-screen steps to cancel your account.
Secondly, Create a New Company
Go to the webpage https://quickbooks.intuit.com/choose-country/.
Here, enter your user ID and password. You can use the same id and password as before.
Also, sign in for the payroll in the Payroll menu if you are using payroll.

Resource - https://bit.ly/3nVaIwf