What do Needs review, Ready to send and Failed mean in the Receipt center?

Needs review is gifts still waiting for a receipt, Ready to send is receipts issued but not yet delivered, and Failed is not tracked yet, so it always shows zero.

The Receipt queue in Receipts mixes gifts that still need a receipt and receipts already issued. The tab tells you which:

Needs review: gifts that show Needs receipt and have no receipt yet. Tick gifts and click Generate, or use Generate receipts for everything waiting.
Ready to send: receipts that are issued but not yet emailed or printed. Click Send all ready to email them all.
Sent: receipts that were emailed or printed.
Failed: Donors doesn't track email delivery failures yet, so this tab always shows zero and "No delivery failures reported."
Voided / corrected: receipts that were voided.

Details

Each Needs review row has a note: "Monthly instalment" for a recurring charge, "Set to an annual receipt" for a donor whose preference is Consolidated annually, and "Over auto-receipt threshold" for everything else, including gifts you recorded by hand.

Click a row to open the gift. Click the receipt number to open the receipt. Click Download to save the rows on screen as a CSV.

If Send all ready can't send some receipts, you'll see how many were sent and that "the rest are still in Ready to send." A receipt for a donor with no email can't be emailed; open it and print it instead.

The panel on the right also checks your setup. "No authorized signature yet" means receipts can't be issued until one is added in Organization Settings → Receipts.