You can download invoices in two places in Billing settings.
From Credit History
Open Billing settings.
Under Usage, click View details.
In Credit History, find the Payment row you need and click Download Invoice.
Rows marked Complimentary credits weren't paid for, so they have no invoice.
From the Stripe billing page
In Billing settings, go to Payment and click Manage payment.
A Stripe billing page opens in a new tab. Sign in with your billing email address.
Open your invoice history and download the invoice you need.
Contract invoices
If your organization is billed under a contract, invoices are sent by email to the billing contact on the contract. Once a contract invoice is paid, it also appears in Credit History with a Download Invoice button.
Can't find an invoice?
Click Get help in Billing settings and include your account email, team name if you have one, and the approximate billing date.