I commonly ship out packages worth over $800, which is the "de minimis" value for the US. This means my package will be hit with customs duties.

Blackship doesn't include HTS codes (a classification system used to determine customs duties to be paid on imports) on their customs forms, and this can cause major delays during shipping as customs agents try to figure out what the correct HTS code is for each declared item so they can get their money. It can be over really simple stuff too, like my previous package being stuck in customs for over a week because they needed to know the material used in a phone strap (which was rubber).

Being able to (optionally) add HTS codes alongside each item on your package customs list would be a big deal for me and other people who ship high-value packages.

Edit 8/7/2023: It looks like Japan Post is going to start requiring HTS/HS codes on customs documentation for packages sent to many European countries starting September 22nd, and to all countries starting March 1st, 2024: https://www.post.japanpost.jp/int/ead/index_en.html

Would be a great time to implement a feature like this!