Hey there majesticcaviar-g,
Thanks for reaching out to us here. QuickBooks Online is a great tool that helps you manage your customer base. It's important that you have the right customers in your account. I can provide some information on customers.
In QuickBooks Online, there isn't an option to delete a customer, but you can make a customer inactive by following the steps in this article. This hides them from your customer list. If a customer is Inactive, all transactions associated with them will remain on your reports that way you don't lose any information or transactions.
If you have any other questions, feel free to reach out here.