In magento, most of the payment gateways like paypal, stripe etc. creates the invoice automatically after capturing the amount. Once an invoice is created its email notification is send immediately. So, once a customer place an order, they gets 2 emails immediately one is for order confirmation and another is for invoice. Both have very minor differences in their content and user treats them duplicate emails. So, we can disable invoice email notification in magento.
Disable invoice email notification in magento
You can disable invoice email from magento backend. Login to magento backend with admin user and go to System > Configuration > Sales > Sales Emails. Now click on the Invoice tab in right section and first option is Enable dropdown with Yes/No values. Select No option and click on the Save Config in right top section.
Now, customer will not get any email notification for the invoice.