Deleting a customer has a number of restrictions. In most cases, you will only be able to make a customer inactive as opposed to deleting them. Deleting a customer or making them inactive is dependent on the following questions.
Are you using QuickBooks Online or QuickBooks Desktop?
Do you want to delete a customer or a lead?
Do you want to delete a customer or a contact?
QuickBooks Online vs QuickBooks Desktop
QuickBooks Online doesn't allow you to remove a customer, whereas QuickBooks Desktop allows it under certain conditions.
If you are on QuickBooks Online, you can only set a customer to Inactive. You will be unable to delete the customer in Method or QuickBooks Online.
If you are on QuickBooks Desktop, you can only delete a customer if the customer has no transactions. If you wish to delete the customer, you need to delete all of their associated transactions first.
Customer vs Customer Lead
There is a small difference between a customer and a customer lead: a customer lead has not synced to QuickBooks yet.
Deleting a customer lead is simple. When viewing a contact in Method, edit the Customer Details and then click the Delete button. If that customer lead has a balance, you will be warned ahead of time, but the customer will be deleted if you accept it.
Deleting a customer that is synced to QuickBooks has a few more restrictions. It is dependent on whether or not you are using QuickBooks Online or QuickBooks Desktop. You can, however, always make a customer inactive.
NOTE: Any transactions associated with the customer will become orphaned if the customer is deleted. For example, any invoices associated with the customer will have its customer field empty after deletion. The invoice itself is not removed.
Customer vs Contact
There is a difference between a customer and a customer's contact. For more information, please check our article What is a Contact?
A customer can have multiple contacts, but a customer must always have at least one contact.
Deleting a contact from a customer who has multiple contacts is simple. When viewing a contact, edit the Contact Details, and the click the Delete button.
Deleting a contact from a customer with one contact can't be done. Instead, you must delete the customer or make them inactive.
NOTE: Any records associated with the contact will become orphaned if the contact is deleted. For example, any activity associated with the contact will have its contact field empty after deletion. The activity itself is not removed.
Can I make deactivate or delete multiple customers?
At the moment, there isn't a way within the stock screens to delete multiple customers, or make multiple customers inactive.
You can, however, do this with customization. If need be, you can view our article Mass Update Records through Batch Processing which will describe how this process works.
However, deleting records on mass is dangerous.
If you delete a customer via customization, you will be unable to bring it back. Furthermore, QuickBooks Desktop may restrict this action if a customer has a transaction and you will get a number of errors. It is recommended to only make customers inactive if you plan on doing them in mass.