I guess it's returned back package.

For a package being returned to China due to a defect, wrong order, or similar non-commercial reason, the core principle is to prove to customs that these are "returned goods" and not a new purchase. The required documents and procedures differ significantly from receiving a new import.

📝 Key Documents for a Returned Package
Your main goal is to provide a complete paper trail that explains the situation. Here are the typical documents you'll need:

Document Purpose & Key Details
Return Authorization (RMA) A critical document. It's an approval number or letter from the seller (e.g., a company in China) authorizing the return. You must obtain this first before shipping the item back. Include this number visibly on the package.
Proof of Original Export To prove the item originally came from China. This can be a copy of the original commercial invoice, air waybill (AWB), or bill of lading (B/L) from the initial shipment out of China.
Commercial Invoice (for Returns) A new invoice stating "RETURNED GOODS – NO COMMERCIAL VALUE" or "RETURN FOR REPAIR". It should list the original invoice number, describe the item, and state a nominal or zero value for customs purposes.
Detailed Packing List Must exactly match the quantity and description of the items being returned to the original export document. Even one extra item can cause problems.
Customs Declaration Form The standard international form (like CN22/CN23). Clearly write "Returned Goods" in the description box and attach the documents above.
📮 Where to Submit and How to Proceed
The submission process depends on who is handling the logistics:

Submit to Your Shipping Carrier: Most individuals submit the documents to the international carrier they are using (e.g., postal service, DHL, FedEx) when they ship the package. The carrier will then file them electronically with Chinese Customs.

Use a Customs Broker or Forwarder: For valuable or complex returns, businesses often hire a China-based freight forwarder or customs broker who can directly manage the declaration and clearance on your behalf.

🏛️ Special Rules for Defective Goods for Repair
If you are returning defective goods to China for repair and re-export, there is a specific, strict process to potentially avoid paying import duties again:

Quantity Must Match: The return shipment must contain the exact same number of items as the original export.

Third-Party Inspection: Upon arrival in China, a third-party inspector may examine the goods to verify they are indeed defective.

Time Limit for Re-export: If approved, you typically have up to six months to have the goods repaired and shipped back out of China. The re-export must match the quantity sent for repair.

Alternative: Paying Duties. To avoid this complex process, you can choose to declare the items as a normal import and pay applicable duties and VAT (often around 12% and 17%, respectively), but this gives you more flexibility.

📋 Quick Summary & Action Steps
Here’s a simple checklist to get started:

Contact the Seller in China immediately. Get their written return authorization (RMA) and the correct return address.

Gather Original Documents. Find the invoice and shipping documents from when you first received the item.

Prepare Return Documents. Create a new commercial invoice marked "Returned Goods" and a matching packing list.

Choose Your Shipping Method. Declare the package clearly with your carrier using a CN22/CN23 form and include all paperwork inside the package.