Please click on the link or scroll down to find information on the following:
Who should allocate Identification Numbers?
Building a GTIN 13
Building a GTIN 14
How to calculate a Check Digit
Keeping Good Records
Notifying Trade Partners
When should I change the Bar Code?
Re-using Numbers
Exporting to the US and Canada
Who should allocate Identification Numbers?
Generally, the organisation that owns the specifications for a product (or the Brand Owner) is responsible for the allocation of the GTIN, regardless of where and by whom, the product is manufactured. In some instances, such as in the manufacture of own brand products or where manufacturing is outsourced, the following may also be responsible for allocating GTINs:
An importer or wholesaler If the importer or wholesaler has the product manufactured in any country under a brand name that belongs to the importer or wholesaler, then they are responsible for allocating the GTIN.
A retailer If a retailer has a product manufactured in any country and sells it under a brand name that belongs to that retailer, then they are responsible for allocating the GTIN.
Some companies produce the same product in different countries or at several manufacturing facilities. In this case the number should be allocated and managed centrally or by just one of the companies or plants.
Building a GTIN 13
In the following example we will allocate an EAN 13 for a fixed weight consumer unit intended to be scanned at the retail point of sale.
The GS1 Company Prefix is the starting point for generating a GTIN 13. In Ireland, the prefix may be 7, 9, or 11 digits long, e.g. 539123456 depending upon the capacity required by the allocating company. The first three digits, 539, indicate that the number was issued by GS1 Ireland and the remaining digits e.g. 123456 uniquely identify the allocating organisation. The full prefix digits should be used comprehensively and as a whole.
Please Note: 539123456 is used for illustrative purposes only. Please refer to your membership documentation from GS1 Ireland for the correct number which has been allocated to your company.
After the Company Prefix you must add an item reference number for the product or service you wish to identify. As the GTIN will be 13 digits in total (12 plus a check digit) the length of the item reference number will vary depending upon the length of your company prefix number.
The item reference number will be:
- 5 digits long if you have a 7 digit prefix
- 3 digits long if you have a 9 digit prefix
- 1 digit only if you have an 11 digit prefix
The length of the item reference number indicates the size of the number bank available. A five-digit item reference number indicates a bank of 100,000 numbers from 00000 to 99999. Similarly a three-digit item reference means that your company has the use of 1000 unique numbers from 000 to 999. An 11 digit prefix indicates a bank of 10 numbers has been allocated to you.
Example: a 9 digit prefix and a 3 digit item reference number:
539 123456 789 where 789 is the trade item reference number.
It is best practice to allocate numbers to your products or services in a sequential manner starting from 0 and working your way up. The numbers allocated should be non-significant and it is not recommended that various parts of the number bank are reserved for use for different categories of product.
The next and final step in completing your full GTIN, is the calculation of the Check Digit which is explained in the section below.
Building a GTIN 14
To generate a GTIN 14 or outer case code simply allocate a new 12 digit number from your number bank as outlined in the section above.
If the case you wish to identify contains fixed weight consumer units, prefix your new 12 digit number with 0 and then calculate the check digit in the standard way.
If however, the case contains variable weight consumer units, prefix the 12 digit number with a 9 and then calculate the check digit.
This fourteen digit number may now be printed as either an ITF 14 or GS1 128 bar code symbol.
How to calculate a Check Digit
The Check Digit is the last, rightmost digit of the number and is based on a mathematical algorithm called the Modulo 10. The check digit is a key control in the accuracy of the GTIN. It is a computer check to make sure the bar code is correctly composed. When a scanner reads a bar code symbol, it will perform the same calculation and verify that the two results match. In this way the scanner knows it has read all the digits of the number correctly.
There are 5 steps involved in calculating the check digit manually.
- Taking the sample GTIN 539 123 456 789, start with the digit on the right side of the number (i.e. the 9) and sum all the alternate digits, reading from right to left: 9 + 7 + 5 + 3 + 1 + 3 = 28
- Multiply the result of Step 1 by 3: 28 x 3 = 84
- Again from right to left sum all the other remaining digit values: 8 + 6 + 4 + 2 + 9 + 5 = 34
- Add the result of Step 2 to the result of Step 3: 84+34 = 118
- The Check Digit is the smallest number, which when added to the result of Step 4, produces a multiple of 10: 118 + x = 120. Answer is 2.
In this example, the next multiple of ten after 118 is 120. Therefore the Check Digit is the difference between 120 and 118, which is 2.
The complete number is 5 3 9 1 2 3 4 5 6 7 8 9 2
If you are generating many GTINs you may wish to use the online check digit calculator which is available on this website.
Keeping Good Records
GS1 Ireland recommends that a proper record should be retained of all allocated GTINs. This record could be in either hard or soft copy. Records may be held on a spreadsheet, in a database or in a hardback notebook. Whatever method is chosen, it must be properly managed in accordance with the rules and procedures of GS1 Ireland and GS1 across the globe.
When managing GTINs, you may find that it is necessary to set up a database to store information about the GTINs or to reference a GTIN against the master product file already existing in your company.
Every user should ensure that their database can record 14 digit GTINs even if EAN/UCC 14 digit numbers are not presently used. This is especially important as future applications may use 14 digits for retail point of sale.
Notifying Trade Partners
As the party responsible for managing the GTINs for your products and services, you are responsible for notifying your trading partners about the GTINs assigned and also details of any changes or deletions made.
This information is used in a wide range of processes including checkout operations, ordering, invoicing and stock control and cannot be carried out correctly if the proper item information is not available.
Comprehensive information should be sent to your customers well in advance of trade commencing, to give your trading partner a chance to process it. The details should include your company name, address and Global Location Number (if applicable), the date, the 14digit GTIN for each traded unit, the full traded unit description, the GTIN for each retail unit and the full product description, including size & weight.
When should I change the Bar Code?
When launching a new product, changing an existing one or running a promotion many people are uncertain whether or not to keep or change the GTIN (bar code).
Follow this link to an online tool which will assist you through the decision making process.
Full details are also available in the First Steps Guide to Bar Coding and the GS1 General Specifications. For further details about either of these publications please contact our Helpdesk on (01) 208 0660.
Re-using Numbers
If a product is deleted from a range, the GTIN may be reassigned to another product if, the product is no longer within the supply chain and a period of no less than four years has lapsed since the product was deleted.
Exporting to the US and Canada
A numbering system, called the Universal Product Code or UPC is administered by GS1 in the United States and Canada.
The number structures and bar code symbols for UPCs are very similar to EAN 13 and EAN 8. The crucial difference however is that the numbers are 12 digits and 8 digits in length.
Prior to January 2005 all product exported to North America had to be marked with a UPC A or UPC E symbol as the software for scanning bar codes at the retail point of sale was configured only to read symbols up to a maximum of 12 digits in length.
A project called Sunrise 2005 was set up back in the 1990's to faciliate the upgrade of retail POS systems to handle EAN 13 symbols. As a result of the completion of this project companies may now export product marked with EAN 13 symbols to North America. This means that companies need no longer apply to GS1 Ireland for a separate UPC prefix. As of October 2004 GS1 Ireland ceased to issue new UPC prefixes. All existing users of UPC prefixes are unaffected by this change.
