Section 321 is a United States Custom and Border Patrol (CBP) Shipment Type that allows for goods (under $800 in value to one end customer) to clear through customs tax and duty-free.
Section 321 Getting Started Guide

Section 321 is a United States Custom and Border Patrol (CBP) Shipment Type that allows for goods (under $800 in value to one end customer) to clear through customs tax and duty-free.
Gain insight into the fulfillment playbook of today’s top D2C brands.
This definitive guide will answer all of your questions and help you to make a better-informed decision.
Questions to ask when looking for an order management system that integrates with Shopify.
Top questions to ask prospective Shopify EDI Partners
Questions when looking for an Inventory Management System that integrates with Shopify.
In the interest of saving you some time, we have compiled some basic questions you can ask prospective 3PL providers.