Container Number vs Bill of Lading vs Booking

Why the three references exist — and why they confuse importers

Container shipping generates three distinct reference numbers that circulate between suppliers, forwarders, carriers, customs agents, and importers. Each serves a different purpose in the shipping lifecycle. The confusion arises because all three can be used for tracking — but they work in different portals, at different stages, and return different information. Knowing which to use when saves hours of frustration.

In South Africa the stakes are particularly high. Durban's free-time window at TPT terminals was cut to 3 days from 1 April 2025 (down from 3.25 days). Cape Town has similarly tight windows. Getting the wrong reference into the wrong system, or calling your forwarder with the wrong number, costs time — and at Durban those hours translate directly into rand.

The container number: ISO 6346 format explained

A container number is the permanent, unique identifier of a physical shipping container — the steel box itself. It is painted in large characters on all four sides of the container and on the top. It stays the same for the container's entire operational life, regardless of which cargo it carries or which carrier operates it.

Container numbers follow the ISO 6346 standard and have a precise format:

So the full container number is always 11 characters: 4 letters + 6 digits + 1 check digit, written as MSCU 123456 7 or MSCU1234567. When you enter a container number in a tracking portal, the system calculates whether the check digit is valid. An incorrect check digit is an immediate sign of a transcription error.

You can find the container number on the packing list, on the B/L once it is issued, in the carrier's booking confirmation once the container is assigned, and physically stencilled on the container itself. A free online ISO 6346 check-digit calculator (several exist) can verify whether a container number you have written down is mathematically valid before you spend time tracking it.

The Bill of Lading number: the shipping contract reference

The Bill of Lading (B/L) is the legal contract between shipper and carrier. The B/L number is the unique reference for that contract. It is issued by the carrier after the cargo is loaded and the B/L is "cut". One B/L can cover one container or many containers shipped together under the same booking.

B/L number formats vary by carrier and are not standardised the way container numbers are:

• MSC: typically alphanumeric, e.g. MSCUA1234567 (may start with the carrier prefix)
• Maersk: typically all-numeric, e.g. 785432100
• CMA CGM: often mixed, e.g. CGM1234567 or FBL1234567
• Hapag-Lloyd: typically starts with HLCU or similar prefix

The B/L number is printed prominently at the top of the Bill of Lading document. It is also in the carrier's booking confirmation email once the B/L is issued, and on the arrival notice your clearing agent receives.

Tracking by B/L number returns the status of all containers in the booking — which is why it is the most useful reference for initial tracking. If your supplier shipped two containers under one booking, entering the B/L number shows both containers, their vessel, and the ETA at Durban or Cape Town.

The booking number: useful only before cargo is loaded

A booking number (sometimes called a booking reference or booking confirmation number) is issued by the carrier when your forwarder or supplier reserves space on a vessel. It is the reference used to arrange the container pickup from the depot, stuffing, and submission of cargo for loading.

Before the B/L is issued — typically before or shortly after the vessel departs — the booking number is the only reference available. Once the B/L is issued, the booking number becomes secondary. The carrier's portal and your forwarder will have both references, but:

• Tracking portals often support booking number searches, but results may be less complete than a B/L search
• The booking number does not confirm that cargo was actually loaded — it confirms only that space was reserved
• If the shipment was rolled (moved to a later vessel), the booking number may be updated but the B/L number will reflect the actual loaded vessel

In practice: use the booking number when chasing your supplier to confirm cargo was loaded. Switch to the B/L number for all tracking once it is issued.

Summary: which reference to use and when

Master B/L vs House B/L — which reference do you have?

If you received your shipping documents from a freight forwarder rather than directly from MSC, Maersk, or another line, you likely have a House B/L (HBL) — issued by the forwarder. The carrier's tracking portal only recognises Master B/L (MBL) numbers. Entering a house B/L number on the carrier's site returns "Not found" even when the shipment is perfectly fine and en route.

Solution: ask your forwarder for the Master B/L number. They must give it to you. Once you have it, all carrier tracking works normally. For LCL (groupage) shipments your cargo is inside a shared container — the master B/L covers the whole container but your house B/L reference is needed for the individual consignment tracking in the forwarder's system.

Practical example: tracking a Durban-bound shipment end to end

Here is how the three references typically appear in a real import scenario — a 40-foot FCL from Shanghai to Durban:

1. Week 1 (before loading): Your supplier shares the booking confirmation. Reference: booking number BKG123456789 on MSC. Use this to confirm the container (MSCU9876543) was picked up from the depot and stuffed.
2. Week 2 (vessel departs Shanghai): Your forwarder emails a B/L draft. The Master B/L number is MSCUA9876543. Track on myMSC.com with this number — the result shows vessel MSC Beatrice, voyage AB123, ETA Durban 2 May.
3. Week 4 (vessel off Durban): ETA passes but no discharge update. Check MarineTraffic for MSC Beatrice — it is at anchor 8 nm off the Bluff. Alert your clearing agent not to book a truck yet.
4. Day 27 (vessel berths, container discharged): Carrier portal updates to "Discharged". Contact clearing agent with container number MSCU9876543 — they query the Durban terminal system using this number to check pickup availability and gate status.
5. Day 29 (gate-out): Clearing agent confirms SARS release; truck is booked; container exits the terminal. The free-day clock (3 days from discharge) was used in full — no demurrage triggered, but only because you planned around the anchorage delay.

Frequently asked questions

My container number has only 10 characters — is it wrong?

ISO 6346 requires 11 characters (4 letters + 6 digits + 1 check digit). If you have 10 characters, you may be missing a leading zero in the serial number, or the check digit has been stripped. Try adding a zero after the four-letter prefix and before the digits, or check the physical container — the full 11-character number is always painted on the door end. You can also use an online ISO 6346 check-digit calculator to verify or reconstruct the correct number.

Can one B/L number cover containers on different vessels?

Technically no — a straight B/L covers cargo on a single vessel. However, if cargo is rolled (moved to a later vessel after the original vessel sailed), the carrier may issue an amended B/L on the same number for the new vessel. This is uncommon but happens. If your B/L tracking shows an unexpected vessel name, check with your forwarder whether cargo was rolled.

Is the booking number the same as the container number?

No. A booking number is assigned when you reserve space on a vessel. A container number identifies the physical box. They are completely different references. It is possible for a booking to have one container number (if only one container is booked) but they are generated independently and follow different formats.

Why does my clearing agent ask for the container number specifically?

Once cargo is at the terminal, all port and terminal systems (including Transnet's NAVIS system at Durban) work with the container number, not the B/L. The customs entry, terminal delivery order, and pickup slot are all linked to the container number. Your clearing agent needs it to query SARS release, check the terminal position, and book the gate-out.

What does the check digit on a container number actually do?

The check digit is a number from 0 to 9 calculated by a specific algorithm from the preceding 10 characters. If you misread one character on the container — for example writing O (letter) instead of 0 (zero) — the check digit will not match the calculated value, immediately signalling a transcription error. Systems that validate ISO 6346 will reject the container number at the point of entry. This is a built-in error-detection mechanism that saves significant documentation errors in high-volume port operations.

Related guides

• How to Track a Container Using a Bill of Lading Number
• How to Track MSC, Maersk & CMA CGM Containers into Durban
• How to Read a Bill of Lading — South Africa
• All container tracking guides →