Shipping Container Number per ISO 6346 Standard: How to Decode, Verify, and Find It

In international logistics, a shipping container number is its "passport" and unique digital identifier. It is by this code that terminals release cargo, customs identifies the shipment, and shipping lines track equipment location worldwide via GPS and EDI systems.

A single typo in a letter or digit can cause a container to get stuck at the port, customs to refuse cargo release, and the cargo owner to incur colossal losses from demurrage and detention fines. In this article, we will break down in detail how a container number is structured, where to find it physically, and why its verification is critical when ordering a container truck or selling the equipment.

How a Container Number is Structured: The ISO 6346 Standard

All shipping containers worldwide are marked in strict accordance with the international ISO 6346 standard. The number always consists of exactly 11 characters (letters and digits) and includes four logical parts.

Let's look at an example number: MSCU 123456 7

1. Owner Code (BIC Code) — 3 letters

This is a unique prefix registered with the Bureau International des Containers (BIC). It indicates the company that owns the equipment.

Examples: MAEU (Maersk), MSCU (Mediterranean Shipping Company), CMAU (CMA CGM), HLXU (Hapag-Lloyd), OOLU (OOCL).

Nuance: If you see a code not registered with the BIC (e.g., made up for a converted storage unit), such a container cannot participate in international sea or rail transport.

2. Equipment Category Identifier — 1 letter

The fourth character indicates the type of equipment:

U (Upright) — standard freight shipping container (the most common option).
J — detachable freight container-related equipment (e.g., a diesel generator / genset for a reefer).
Z — trailers, chassis, and automotive superstructures.

3. Serial Number — 6 digits

The unique sequential number of the container within a specific owner's fleet (e.g., 123456). It is assigned at the manufacturing plant during production.

4. Check Digit — 1 digit

Located in a separate box at the very end (in our example, it is 7).

Purpose: It is calculated using a complex mathematical formula (using powers of 2 for each letter and digit). This digit is needed to automatically verify the correctness of the entire number entered into the computer systems of a port, customs, or rail terminal. If a dispatcher makes a mistake entering even a single character, the system will throw an "Invalid check digit" error and block the processing.

Where is the Number Physically Located on a Container?

The number is duplicated in several places so it can be read under any conditions (even if the container is stacked high on a vessel or rail flatcar):

Doors: On the right and left door leaves (usually at the top). This is the primary location for drivers and warehouse staff to read.
Side Panels: Painted in large letters on the longitudinal walls (often on both sides). Needed for crane operators and inspectors.
Roof: On the top surface (for reading by drones or cameras on high terminal masts).
CSC Plate (Safety Approval Plate): A metal nameplate on the left door leaf. Here, the number is stamped mechanically. This is the container's primary legal document.
Documents: Bill of Lading, international CMR consignment note, rail waybill (SMGS/GU-29), invoice, and packing list.

The Risks of Errors: The Cost of a Single Typo

Why do logistics managers and customs brokers get so nervous about container numbers?

Terminal Release Denial: If the removal application (gate pass) contains an incorrect number, the checkpoint system simply will not open the barrier for the container truck. The truck will sit idle, and the storage fine counter (demurrage) will keep ticking.
Customs Issues: Customs verifies the number in the declaration against the actual number on the seal and doors. A one-digit discrepancy = an administrative case, full cargo inspection, and delays lasting weeks.
Buyback Issues: If you decide to sell us a container, but the number on the door does not match the number on the CSC plate or in your title documents, this is a sign of "altered" numbers or a potentially unlawful origin of the container. Such containers are not accepted for buyback.

How We Handle Container Identification

We ensure legal and physical safety at all stages of working with equipment:

During Road Transport: When our drivers arrive at a terminal (e.g., Kolyadichi, Stepyanka, Brest) with a container truck, they are required to verify the number on the pass against the actual number on the doors and the seal. This eliminates the risk of taking someone else's cargo.
During Container Buyback: Before a transaction, we conduct strict identification. We verify that the number on the body matches the CSC plate and your documents. We only buy legally clean containers with readable, unaltered BIC codes.
Documentation Assistance: If you have lost your container documents, we will advise you on how to restore the data using the owner's BIC code to legally process the sale.

How to Order Transportation or Container Buyback?

Contact us, provide the container number (or send a photo of the doors and CSC plate), and we will instantly identify its type and dimensions, select the right transport, or calculate the buyback cost.

Phone: +375 333 888 112

Mobile: +7 (912) 251-37-46

Email: Minskdepot@mycontainers.ru

*Information on this page does not constitute a public offer.

Answers to questions

What should I do if the number painted on the door does not match the number on the CSC plate?

Legally, the number stamped on the metal CSC plate is the valid one. A discrepancy may mean the container was in a serious accident, the doors were replaced, or the numbers were "altered." Such a container will not pass customs control, and we can only buy it at a minimal price in the "As Is" category (as scrap metal or for dismantling).

How to calculate a container's check digit?

Each letter of the Latin alphabet is assigned a numerical value (from 10 to 38). This value is then multiplied by 2 raised to the power of the symbol's position. The sum of all resulting values is divided by 11. The remainder of this division is the check digit. This is not calculated manually; online BIC calculators or built-in algorithms in logistics software are used.

Does a change of ownership affect the container number?

Yes. If a shipping line sells a container to a leasing company or a private investor, the new owner must re-register the equipment with the BIC, apply their own Owner Code, and change the number. The old number is painted over.

Can I paint over the container number when repainting it for use as a warehouse?

If the container is used solely as a stationary warehouse on private property and is not going anywhere, you can paint it however you like. However, if you plan to sell it in the future or transport it by rail/road, the number (including the BIC code and serial number) must be restored and clearly legible.

What do the prefixes MAEU, MSCU, and CMAU mean?

These are the BIC codes of the world's largest shipping lines: MAEU — Maersk, MSCU — Mediterranean Shipping Company, CMAU — CMA CGM. If you see such a prefix, it means the container belongs to a global operator and is likely under lease or charter.

Do you buy containers with unreadable or faded numbers?

If the number on the body has faded due to time and sun, but it is clearly legible on the CSC plate and you have documents proving ownership, yes, we will consider the buyback. However, if the plate is missing or the number is unreadable anywhere, the transaction is impossible due to the risk of the equipment having a criminal origin.

Where is the container number indicated on a CMR consignment note?

The container number must be entered in the field designated for identifying the vehicle or cargo unit (usually box 17 or in the free-text fields for special remarks), and it is also duplicated in the domestic waybill (TTN).

What are the prefixes TGHU or CSLU?

These are the BIC codes of major leasing companies (e.g., Touax, Triton, Textainer, CAI). Most containers in the world are owned not by the shipping lines themselves, but by lessors who lease them out.

Does a container truck driver need to know the container number?

Absolutely. The driver must verify the number against the trip sheet and terminal pass before securing the container with twistlocks. Loading the "wrong" container by mistake is a criminal offense (theft or misappropriation).

How does customs verify the container number during export/import?

A customs inspector physically goes to the container (or uses surveillance cameras at the terminal), reads the number from the doors, and cross-checks it with the number declared in the electronic customs declaration. In case of a mismatch, the cargo is sent for a full inspection with seal breaking.