In Billing > History tab, you'll find monthly invoices of your website subscription.
To filter your history list by year, click on funnel icon locate at right top of invoice list. Note that, your invoice is generated starting from your first website added month.
By clicking on eye icon under Action column, you'll get detailed description of particular invoice. You can download PDF version using download button inside same column.
If you have any concern, feel free submit on support portal.