So you're shipping an international order, and you see the field Harmonization Code on the Customs Declarations section of the order detail popup. What is it for?
The purpose of a Harmonization Code (also referred to as "Tariff Code", "Customs Tariffs", "Harmonized Tariff Codes", and "Harmonized System Code") is to expedite the shipping process for international orders, as they are used for tax assessment purposes. This is a system used to trade most of the merchandise that is sent internationally and is a universal economic language and code for your goods.
Once an order reaches an international border, these codes will help the customs office to identify what it is that you are shipping. So it is recommended to have your harmonization codes listed and properly-identified at time of label creation.
If you would like to update your product records to include the correct harmonization code, you can follow the steps in this article to update the product records.
For a full list of Harmonization Codes, head here.