Your Invoice
One invoice per auction, frozen when the auction closes, under Account → Invoices.
You get one invoice per auction, listing every lot you won there. It is created as lots close and finalized once the last lot in the auction has closed; at that point it gets a number, is frozen, and is emailed to you.

Find every invoice under Account → Invoices. Each has a Download PDF button for a printable copy on the house's letterhead, with your bidder ID and paddle number, every lot, the totals, and what has been paid. The email announcing the invoice links to the PDF too. The PDF is remade whenever a payment or a shipping detail changes, so the copy you download is always current; if you open it in the seconds after a change, it may ask you to try again shortly.
Each shows the lots, hammer prices, premium, tax, what has been paid and what is owed, and whether it is for pickup or shipping.
The premium and tax rates on an invoice are the ones in force when it was created. A house changing its rates later never changes an invoice you already have.