Are you currently on a paid plan?
If you are currently on a paid plan, go to your account settings and click on the "Access your billing information" link. Note that if you paid with paypal, you can only get invoices/reciepts from Paypal.
Are you currently on the free plan, and looking for past invoices?
If you paid for your subscription with a credit card, please contact us via the chat window with the payments you would like an invoice. If you paid with Paypal, you can only get invoices/receipts from Paypal.