Users should be able to access their monthly invoices by going to their Billing page.
To get to the Billing page, first users must login to their Seller Labs account. Click on your email on the top right corner of the page and from the dropdown click on Account. Lastly, you will want to click on the Billing tab from the top of the page. You can view each invoice under "Payment Activity". If you click "View Receipt", in the Action column, it will give you a full page version of the invoice and allow you to download a copy for your records.
For information on changing your billing address, please visit: https://support.sellerlabs.com/seller-labs-account-general/how-can-i-change-the-address-used-for-my-invoices