If you are a business owner who uses QuickBooks Online to manage your finances, you may need to add a sub-customer to your account in order to track payments and invoices for a particular project or client. This can be especially useful if you are working with a large client who has multiple divisions or departments that need to be tracked separately. Knowing how to add a sub-customer in QuickBooks Online can help you keep your financial records organized and up-to-date.