A manifest is a scan form that generates a barcode, allowing you to check all your packages in at once. Ship Thrifty automatically generates a manifest for your USPS shipments, reducing drop-off or pickup time by 90%. USPS scans a single form, and all your packages are checked in at one time, rather than scanning each label individually. Most people split orders into groups of 300 or fewer and may create multiple manifests to make the batches easier to handle.