When your supplier in China finishes loading a shipping container, they should secure its doors with a container seal. Before the truck leaves the loading site, you need to know who applied the seal and whether its number matches the shipping documents.
A container seal is a numbered, tamper-evident device used to help identify unauthorized opening of a freight container. It doesn’t guarantee cargo security, but it provides an important record of the container’s condition during transport.
For importers shipping from China, knowing what to check before departure can help prevent document discrepancies and avoid confusion at destination.
What Is a Container Seal?
Most international FCL shipments use a high-security bolt seal, which is typically attached to a container door’s locking mechanism after loading. Cable seals are another option, depending on the carrier’s requirements.
These devices provide evidence of possible tampering, but they cannot prevent every unauthorized entry or replace other cargo security measures.
Who Seals the Container When Shipping from China?
The party responsible for loading the container normally applies the seal once loading is complete.
If your Chinese supplier loads the container at its factory, the supplier or loading team typically seals the doors. If loading takes place at a warehouse, the warehouse operator may handle this step.
Exact responsibilities depend on the shipping arrangement and carrier instructions.
Before the container leaves, ask the loading party for:
- A photo of the closed container doors
- A clear photo of the applied seal and its number
- The container number for comparison with the booking details
Make sure the loading party records the correct seal number for the shipping documents.
How to Check the Shipping Container Seal Number
A shipping container seal number is the unique combination of letters or digits printed or engraved on the seal.
It is not the same as the container number.
| Container Number | Seal Number | |
|---|---|---|
| Identifies | The container | The security seal |
| Where to find it | Marked on the container body | Printed or engraved on the seal |
| Changes after seal replacement | No | Yes |
The loading party records the seal number, and the shipper provides it in the Shipping Instructions when required. The carrier may then include it on the Bill of Lading (B/L).
Before departure, compare the number on the physical seal with the Shipping Instructions. Once the B/L is available, check that the number matches.
If you find a discrepancy, contact your supplier or freight forwarder before accepting the documents as correct.
Container Seal Requirements for International Shipping
Container seal requirements vary by carrier, destination, customs regulations, and applicable cargo security programs.
ISO 17712 sets standards for mechanical freight container seals, including three security classifications: indicative (I), security (S), and high-security (H).
International FCL shipments commonly use high-security seals. Some security programs, including the U.S. Customs Trade Partnership Against Terrorism (CTPAT), also impose specific requirements on participating businesses.
Before loading, confirm:
- The carrier’s accepted seal type
- Whether a high-security seal meeting ISO 17712 is required
- Who will provide and apply the seal?
- How the seal number must appear in the shipping documents
Not every bolt seal meets ISO 17712 requirements. Check its classification and supporting documentation when necessary.
What If the Container Seal Number Doesn't Match?
A mismatch may result from a recording mistake or an authorized seal replacement. It does not automatically indicate cargo tampering.
Before departure from China: Contact the loading party or freight forwarder. Compare the seal photo with the original records and correct any affected shipping documents.
After shipment: Ask the carrier or your forwarding partner whether customs or another authorized party opened the container and replaced the seal.
If a replacement occurred, keep the relevant inspection records and the new seal number. Do not assume that the original number should still match after an authorized replacement.
What If the Container Seal Is Broken at Destination?
If the seal is broken or missing when the container arrives, do not open it immediately.
- Take photos of the seal and container doors.
- Contact the carrier or freight forwarder to check whether customs or another authorized party opened the container.
- Keep the relevant records and inspect the cargo for damage or shortages when permitted.
Follow the carrier’s and local authorities’ procedures before removing the seal or opening the container.
Before Your Container Leaves China
You do not need to manage every loading operation yourself, but you should know which details to confirm with your supplier.
For an FCL shipment, check the container number, seal number, loading photos, and Shipping Instructions before departure. If a seal changes, make sure the responsible parties record the replacement correctly.
For LCL cargo, the consolidator generally manages the seal on the shared container. Your individual shipment may not have a separate container seal number.
Shipping a Full Container from China?
The correct seal number is just one part of preparing an FCL shipment. Your loading details and shipping documents must also match the actual cargo. ASLG provides FCL freight forwarding services from China to destinations worldwide.
