A container seal is a small device that directly links the container’s physical condition with data in the Shipping Instruction, bill of lading, manifest, handover records and Customs declarations. A single wrong character can pause document release, handover or declaration processing while the parties verify the discrepancy, amend data or establish whether the container was legitimately opened. This article explains what a seal does, common seal types, the data points that must be reconciled and the proper response when the physical seal number differs from the documents.

Operational update: 21 July 2026 · Scope: FCL container cargo and sealed movements

QUICK FACTS

A seal is a one-time control indicator

It is attached to the container door, carries a unique identifier and normally must be cut or broken to open. It indicates possible interference but does not by itself prove the contents are intact.

The seal number belongs to a specific container

Every container line must carry the actual seal number for that container—not another container’s seal, a planned number or a seal that has already been replaced.

Mismatches have two broad causes

They may be clerical, or they may reflect resealing, inspection, repair, unauthorized opening or a container mix-up.

Never “edit it to make it match” informally

Preserve field evidence, establish who applied or changed the seal, notify the parties and amend records only through a traceable process.

Illustration for What Is a Container Seal? Risks When the Seal Number Does Not Match the Documents — Illustration of the logistics topic, document or operation discussed in the article.

SCOPE OF APPLICATION

This guidance primarily covers full-container-load shipments by sea, road, rail or multimodal transport. It is also relevant to transit cargo, bonded movements and shipments carrying shipper, carrier, Customs, veterinary or other official seals.

It does not replace a carrier’s tariff or procedure, terminal rules, Customs instructions, inspection-agency requirements, insurance conditions or national security programmes. Open-top, flat-rack, tank and other special equipment may be subject to different sealing arrangements.

KEY TERMS

Term	Meaning	Operational role
Container seal / Security seal	A numbered device fitted to the container door-locking mechanism.	Connects the physical closure condition with transport-document data.
Seal number	The alphanumeric identifier printed or engraved on the seal.	Must be accurately recorded in SI, B/L and applicable declarations.
High-security seal	A mechanical seal meeting the ISO 17712 high-security classification; bolt seals are common, but the specific product must meet the applicable technical classification and route/carrier requirements.	Improves resistance to interference and tamper evidence, but does not guarantee the contents are intact.
Shipper seal	A seal applied by the cargo owner, shipper or stuffing facility.	Often the first seal number submitted in the Shipping Instruction.
Carrier seal	A seal supplied or applied by the carrier or its agent.	May replace or supplement a shipper seal under carrier procedures.
Customs seal	A seal applied by Customs while cargo is under supervision.	Must not be treated as an ordinary commercial seal; opening or replacement requires authority.
Resealing	Applying a new seal after the previous seal was legitimately cut or replaced.	Requires the reason, time, responsible party and old/new seal numbers to be recorded.

NATURE AND OPERATING MECHANISM

A seal is one link in the control chain, not an absolute guarantee

A seal lets the consignee and control parties compare the container-door condition with previously recorded data. An intact seal with a matching number is a positive continuity signal. It does not, however, certify cargo quantity, quality or contents, nor does it eliminate every possible method of interference.

Seal data starts at the stuffing point

After stuffing, the responsible party should read the number back, photograph the seal and container doors and record it in the stuffing report or internal system. That data then flows into the Shipping Instruction, draft and final bill of lading, manifest and relevant declarations. A source-data error can therefore spread throughout the document set.

Every seal change must create a new audit trail

A seal may be legitimately replaced after Customs or quarantine inspection, security examination, door repair or a carrier instruction. The control objective is not that a seal can never change, but that every change is evidenced and synchronized across the records.

MISMATCH SCENARIOS AND RISKS

Indicator	Common cause	Risk level	Possible impact	Priority control
One or two characters differ while the physical seal is intact	0/O, 1/I, transposed digits or copied from the wrong container line.	Medium	SI/B/L/manifest amendment and document or delivery delay.	Verify source photographs and seal log; amend formally.
Physical seal is completely different from the B/L	Resealing after inspection, repair or an unrecorded change.	High	Verification request, incident report, physical inspection or cargo hold.	Reconstruct chain of custody and obtain resealing evidence.
Seal is broken, loose, missing or shows cut/weld marks	Damage, incorrect handling or unauthorized interference.	Very high	Shortage/tampering suspicion, insurance claim or security investigation.	Do not open further; arrange joint inspection or survey.
Several seals are present but only one is documented	Additional carrier, Customs or specialist seal.	Medium–high	Wrong seal checked or an incomplete opening record.	Identify seal type, position and applying authority.
Seal number is correct but attached to the wrong container	Container–seal lines were swapped within one booking.	High	Incorrect manifest/B/L, misdelivery and Customs risk.	Check the container-number–seal-number pair, never each field alone.
Documents contain a planned seal number	The issued seal was changed during stuffing.	Medium	B/L and manifest no longer reflect the actual closure.	Finalize data only after the seal is fitted and photographed.

Note: the risk levels in this table are internal operational priorities, not statutory offence categories or legal penalties.

DOCUMENTS AND DATA TO RECONCILE

Record	Typical issuer/preparer	Data to check	When used
Seal issue sheet / seal log	Warehouse, factory, depot or carrier	Seal number, issue date, recipient and intended booking/container	Before stuffing and during trace-back
Stuffing report / photographs	Stuffing facility, supervisor or surveyor	Container number, seal number, time, door and seal condition	Immediately after sealing
Shipping Instruction	Shipper or forwarder to carrier	Container–seal pair, seal type and number of containers	Before SI cut-off
Draft B/L and final B/L/Sea Waybill	Carrier or NVOCC	Container number, seal number, packages and weight	During draft approval and issuance
Manifest / cargo declaration	Carrier, NVOCC or agent	Container and seal data from the transport document	Before filing cut-off and during amendments
EIR, gate-in record and terminal events	Depot, terminal or carrier	Container, gate-in time, equipment condition and seal if recorded	At physical handover
Inspection/resealing report	Authority and witnessing parties	Reason for opening, old/new seal, time and signatures/confirmation	Whenever a seal is legitimately cut or replaced
Delivery and seal-check record	Consignee, receiving warehouse or surveyor	Arrival seal, condition and opening time	Before opening at destination

Mandatory control point: reconcile the container number–seal number pair. A valid seal number attached to the wrong container is still incorrect data.

CONTROL AND RESPONSE PROCESS

Step	Input	Key action	Record to retain
1. Pre-application check	Unused seal and stuffed container	Dual-read or scan the number; confirm the seal has no damage.	Seal log and issue evidence
2. Apply and confirm	Container and seal numbers	Fit at the correct locking point; pull-test; photograph doors, seal close-up and container number.	Timestamped photos and stuffing report
3. Transmit data	Source photos and report	Enter the correct container–seal pair into SI; restrict edits and retain change history.	Cross-checked SI
4. Approve documents	Draft B/L and manifest draft	Compare with the source images, booking and container list.	Approval or amendment request
5. Check at handover	Physical seal and current documents	Inspect before cutting; independently read and photograph the number.	Seal-check or receipt record
6. When a mismatch is found	Physical condition, documents and event history	Where safe and consistent with the applicable process, pause custody acceptance or opening; photograph the condition, note the discrepancy on the documents, and alert the tendering party and shipper. Notify Customs or law enforcement where required by law or procedure, and do not proceed until the discrepancy is resolved.	Incident notice, annotated documents and field evidence
7. Classify and correct	Source evidence and party responses	Separate clerical error from possible tampering; amend documents or arrange joint inspection/survey; record any new seal.	Conclusion report, amendment and chain of custody

COMMON ERRORS AND CONSEQUENCES

Checking only the B/L and not the physical seal

The B/L may contain earlier data. The final operational check is the seal fitted to the correct container at handover or before opening.

Cutting the seal “to check quickly”

Where the number differs or the seal looks abnormal, unilateral opening can destroy evidence and weaken claims. Obtain instructions and document the opening with the relevant parties.

Recording only the new seal after resealing

This breaks the audit trail. The file should connect the reason for opening, witnesses, old seal, new seal, time and observed cargo condition.

Confusing a commercial seal with a Customs seal

They have different roles and authority. A Customs seal must not be removed, replaced or overwritten as if it were an ordinary shipper seal.

Submitting amendments too late

Changes after SI or manifest cut-off, or after B/L issuance, may cause fees, delays and additional verification. Seal data should be finalized before SI submission and rechecked at draft approval.

AUTHORITATIVE SOURCES

Source	Role	Use in this article	Status/note
ISO 17712:2013 – Freight containers — Mechanical seals	International standard for classification and acceptance of mechanical freight-container seals.	Mechanical and high-security seal concepts.	Confirmed by ISO in 2023; current at the update date.
WCO SAFE Framework 2025	WCO supply-chain security and trade-facilitation framework.	Seal inspection at each custody change; comparison against cargo documents; response to missing, tampered or different-number seals.	Calls for discrepancy notification and notation, authority notification under national law, and documentation of any replacement seal after resolution.
IMO/ILO/UNECE CTU Code 2014	Global code of practice for packing and handling cargo transport units.	Stuffing, handover and CTU-control context across the intermodal chain.	Non-mandatory guidance unless incorporated into applicable law, contracts or procedures.
Maersk – Container seal numbers	Carrier operational guidance.	Correct SI entry and comparison with the B/L at destination.	Carrier/local requirements may vary.
Vietnam Circular 50/2018/TT-BTC	Information fields and declaration forms for inbound, outbound and transit means of transport.	In applicable forms, the container seal number must be entered fully and accurately from transport documents; sealed container cargo is a case requiring seal data.	Issued 23 May 2018 and effective 5 June 2018; check amendments or replacement at execution time.
Draft Circular replacing Circular 50/2018/TT-BTC	Draft published by Vietnam’s Ministry of Finance for consultation.	Monitoring source for possible changes to declaration data fields and forms.	Published 14 May 2026; it is a draft and is not an applicable legal instrument.

ISO 17712 WCO SAFE 2025 IMO CTU Code Maersk guidance Vietnam Circular 50/2018 Draft replacement of Circular 50

FAQ

The seal is intact but differs from the B/L. May the container be opened?

Do not automatically accept custody or open the container. Photograph the condition, note the discrepancy on the documents, alert the tendering party and shipper, and ask the carrier/forwarder to verify any resealing history. Notification to Customs or law enforcement and the timing of opening must follow applicable law, handover terms and competent-party instructions.

Does a one-character error prove cargo loss?

No. It may be a data-entry error, but it still requires verification against source photos, seal logs and transport events.

Must the Packing List show the seal number?

There is no universal rule for every trade. Seal data is generally most critical in SI, B/L and transport declarations; include it on the Packing List only when the process, contract, L/C or parties require it.

Can a container carry two seals?

Yes, for example a shipper seal plus a carrier or Customs seal. The type, position and applying party should be documented.

Who submits the seal number to the carrier?

Usually the shipper or a forwarder acting for the shipper enters it in the Shipping Instruction, subject to the service contract and booking process.

Does inspection resealing make the B/L incorrect?

The transport records should be updated when the current seal differs from the issued data. Keep the inspection and resealing record to prove the event chain.

Does ISO 17712 compliance make tampering impossible?

No. The standard strengthens security performance and tamper evidence, but effectiveness also depends on seal issue control, storage, application, documentation and inspection.

APPLICATION NOTE: A conclusion on a seal mismatch must be based on the physical seal, door condition, photos and records at custody points, resealing history, carrier terms, Customs requirements and the shipment file. Do not rely on a single B/L copy or isolated data field. Risk levels in this article are internal prioritization aids and do not replace a determination by a competent authority.

TGIMEX IMPLEMENTATION SUPPORT

TGIMEX helps businesses turn the article into a shipment-ready checklist, covering input-data review, dossier preparation, milestone control, and coordination with the relevant parties.

Convert guidance into checks

Assign an owner and deadline to every operational control point.

Reconcile shipment data

Compare booking, transport, commercial, customs, and delivery evidence.

Manage operational risk

Record discrepancies, actions, and decision evidence to prevent recurrence.

Discuss your shipment dossier

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