When you have items that you need to check in, but haven't received an invoice or packing list from your distributor yet, you can create a CSA invoice for that distributor and add items as "overages" by clicking the ADD OVERAGES button at the top of the page and then checking the invoice in like normal.
 
In some cases, you may receive partial shipments before getting your invoice from your distributor, and you want to get that product put out right away. For example, you may receive Lunar reorder shipments well before they supply you with an invoice to check in, and then you receive your weekly comics a few days later after the invoice has been posted at Lunar.
 
If this happens, once you load the official invoice from your distributor, make sure you remove any lines you've already received on the invoice that you created using the overage button before reporting damages for the newly-created invoice.