If you have an annual subscription, this invoice will be sent by e-mail once a year.
If you have a monthly subscription with credit card or PayPal, you will find your invoices in your online account.
Click on "more" >> Billing & Invoices
Scroll down until you see the link "View and print your invoices here" and click on it.
In the list, look for the invoice you need, and click on "view".
TIP: If you want to save this invoice as a PDF, or if you want to print it, press CTRL + P, or click on "print" in your browser menu and choose the "print to PDF" option.