Stora does not automatically send your customers paying by card an invoice each month. However your customers can login via the "My Account" link at the top of your website, and view all their invoices by pressing the "View payment details" button.
They can then download press the open icon in the Billing History section to open a PDF of each invoice, and download should they wish.
How to automatically email all your customers an invoice each month
It is possible to send these invoices each month direct to your customers via Stripe, here's how:
Login to Stripe, and visit your subscriptions and emails settings page
Locate the "Manage invoices sent to customers" section, and turn on "Email finalised invoices to customers". Your customers will now be sent invoices on their billing day