If you ship a large number of packages at once, the Post Office will ask you to print out a SCAN Form (also known as a shipping manifest). A shipping manifest is a single sheet of paper that contains a list of all the shipments you'll be sending. Shipping manifests are not a perfect technology, and it will make your life a lot easier if you understand a few key points on how they work.
The most important thing you need to know about shipping manifests is what orders will be included on your manifest. When you select the “Print Shipping Manifest” option, all orders with a ship date greater than or equal to the current date will be included. Orders with a ship date in the past will NOT be included. Therefore, please generate your manifest on or before your earliest ship date of orders you would like to include; the cutoff time is 8 pm PST or 9 pm PDT.
Let’s say you have a big sale on Saturday afternoon, and print out all the labels that evening. You decide to include these packages with any additional ones you might end up sending early next week. This scenario works for a single manifest as long as you ensure the packages from Saturday have a ship date greater than or equal to the date you plan on generating your manifest for all packages. If you don’t mind having more than one manifest, you can also create your manifest on Saturday and find it in "Your Recent Manifests” list to print within 7 days of creation.
The second thing you should be aware of is how the manifest date is set. The manifest date is equal to the latest ship date of all orders included.
Another important thing to know is that a manifest being created with the same manifest date as another will be grouped together in a single manifest, i.e. one file to print.
And to reinforce again -- orders with a ship date in past will NOT be included on your manifest, and you have have 7 days to find previously created manifests to print.
Finally, remember that it's OK to provide the Post Office multiple shipping manifests if you don’t get all your orders into your first manifest attempt.