Any invoice can be found within the Reports & Statistics area, accessed through the profile dropdown in the top right of the screen. From here you can access any invoices and CSV transactions associated with the account. This section does require a secondary login to be entered, which is a different set of details to the main account.
If your account is not set up to receive invoices online then you will need to contact our helpdesk at firstname.lastname@example.org. They will be able to help update your account to ensure that you receive your invoices online.