The project owner is the person responsible for the billing and subscription. If you are the project owner you can find a list of all your invoices avaliable to download as PDFs here:
Settings > Your Account > Billing & Invoices
New invoices are also emailed to you when they are issued.
Send invoices to a different email address
We know that its often important to send invoices to your accountants or an alternative team member. By default all invoices get emailed to project owner.
If you need to change this, just click Edit at the top of the Invoices section in Settings > Your Account > Billing & Invoices