About container prefixes

What is a container Prefix?

All containers have a prefix followed by a serial number which taken together are generally referred to as the container number. This number enables operators and shippers to identify and track equipment which is used in the movement of cargo. The prefix and container numbers are also used on all documentation for shipping and custom clearance and in many instances in Letters of Credit (LCs).

The number can be found on each side of the container, the roof, the inside panels and is also stamped on the CSC Plate of the container.

The term prefix customarily refers the first 4 letters also known as the alpha prefix and is usually attached to a line or asset owning entity. It should be noted that while the prefix might give an indication as to who owns or controls a container it does not constitute a title to the container (the CSC plate usually lists the owner’s name).

Lets look at a container number in more details. A CSI unit might be numbered as 200082 :

Container prefix breakdown, CSIU Boston MA

CSI Container Prefix Breakdown

The above includes these four components:

  1. The Owner code consisting of 3 capital letters must be unique and registered with the International Container Bureau (BIC). If absent, the container cannot be identified.
  2. A Product group code consisting of one capital letter U, J or Z (U – for all freight containers // J – for detachable freight container equipment // Z – for trailers and chassis)
  3. A Registration number (or serial number) consisting of only 6 digits.
  4. The Check digit always consists of a single-digit number and is highlighted in a box. This is to verify the owner code, product group code and registration number were accurately transferred. No container number will be accepted in a data processing system if the check digit does not match. This was built in to ensure that a number of transmission errors cannot cancel one another out.

 How do we calculate a Check Digit?

Although the system has been around for quite a while, the check digit is still a mystery to a lot of people in our industry.

Below is a table that will enable you to calculate a check digit and make sure that your container is properly prefixed.

Snapshot of check digit generating formula sheet

Container Prefix – Check Digit Generating Formula Sheet

A numerical value is assigned to each letter of the alphabet, beginning with 10 for the letter ‘A’. (”11” which is a prime number is left out of the value assignments as a specific role has been reserved for it).

The value of each letter is then multiplied by a multiple (all powers of 2) and all added together to form a total (Total1). That total is then divided by 11 (the prime number we just talked about…). You then take the integer portion of the result of that division, multiply it by 11 and deduct that from your Total1 to obtainer your check digit… Guess that language reminds you of some classes you may have taken a long time ago.

As the above table shows, applying this formula to CSIU200082 will give you 0 (zero) as a check digit.

If you want an excel spreadsheet that can do all this for you just drop us a note, we will be happy to share it with you.

 Why should I care about the container prefix ? and the container check digit ? What do I need to look out for  ?

There are two things you want to make sure of are:

1)      that the prefix on your container is valid and registered with BIC (Bureau International des Conteneurs).

International customs regulations require containers to carry an ISO COMPLIANT CONTAINER MARKING in order to be eligible for the transportation of goods under custom seal and to be compliant with ISO defined markings prefixes have to be registered…

While most customs officials are not too particular on this subject, you will find countries where officials INSIST that the prefix used be REGISTERED with BIC.

Prefixes like XXXU and NONU have often been used, but by doing so you are putting yourself at a risk of being found non-compliant. While most of the time the prefix registration will not be a problem… it could…

Believe me you don’t want to have to re-prefix a container while it is on its way under a Bill of Lading (BL) and in the control of customs halfway around the world (we have learned the hard way). This can be especially problematic if an LC is used for the cargo in that container…

 2) that the prefix on your container is not that of the line you are shipping with.

Shipping line computer systems manage the containers based on prefix and number.  If you ship a shipper owned container (SOC) with a line whose prefix is on the container, the computer systems might recognize it as one of its own containers rather than a SOC – SHIIPPER owned container.

The main problems that could result from this confusion could be improper tariffs being used for the container or the container being improperly handled at destination and returned to the line by the consignee or the trucker

If you had any questions that were not answered by this article please do not hesitate to contact us, we will be happy to answer any questions.