What is the International Letter Code System?

The international letter code system is a standardized method of identifying cattle based on year of birth. Each year is associated with a letter of the alphabet. For example, the next few years have been assigned the following letters:

  • 2018: F.
  • 2019: G.
  • 2020: H.
  • 2021: J.
  • 2022: K.
  • 2023: L.
  • 2024: M.
  • 2025: N.
  • 2026: P.
  • 2027: R.
  • 2028: S.
  • 2029: T.

Note that four letters are excluded from the international letter code system:

  • I.
  • O.
  • Q.
  • V.

Letters count back to 1969, the first A year, when the system became popular, and have been rotating ever since. Every time Z is reached, the rotation starts over at A.

Using the Code

The international letter code system is typically paired with other identification numbering systems to provide more specific information that differentiates calves born in the same year. Examples include:

  • Adding numbers to indicate order of birth. Thus the first calf of 2018 would be F01 (or F001 if more numbers are needed), while the second calf of the year would be F02, the third F03, and so on.
  • Incorporating the date of birth. So a calf born on March 15, 2018, would be identified as 315F.
  • Combining the letter code with the month and order of birth. In this variation, the first calf of March 2018 would be 301F, while the second calf of the month would be 302F.
  • Giving the calf the number of the cow. This works best in systems where the calves are sold instead of kept on the farm. If cow B050 has a calf in 2018, her calf will be F050.
  • Numbering cattle in order of birth or acquisition. In this case, the 50th cow on the farm would be F050 and the 51st would be F051.

Some cattlemen put the numerals before the letter for male calves (001F) and after the letter for female calves (F001). Others switch the order to distinguish between calves they co-own and calves they own by themselves.

Animals may be identified with their code by means of ear tags, tattoos, or brand marks. Some level of duplicate identification is commonly recommended to avoid accidental lost identity. For instance, a calf might be tagged in both ears or tagged in one and tattooed in the other.


The most important thing when choosing an identification system is to have a clear, consistent method of distinguishing one animal from another. Which of the variants listed above will work for you depends on the type of information that you will need to be able to see at a glance.