Users should be able to access their monthly invoices by logging in to their Seller Labs Dashboard.
From the left side menu, select Settings > Billing. 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