I am making a trip across the border to pick up an item and as I am going will bring some large and heavy items with me to ship them directly with USPS - about 10-12 items. All the items are under $800 and in total under $2.500US so they qualify as informal entry.
Aside from the invoices and a manifest with the name, address, description and value, do you know if there is an official US form that needs to be filled in?
I have been searching and it may be CBP Form 7501 but it seems aimed at companies.