A code of accounts is an essential tool in the essential management of any project as it allows for the ability to easily distinguish multiple components of a project without need to remember lengthy names or terminologies. Specifically, a code of accounts is a unique lettering or numbering system in which letters or numbers are assigned to each unique component of the work breakdown structure. These unique identifiers should remain constant through the life of the project and should not be recycled it at all possible. If the desired code of accounts character is a letter, and more than 26 components require coding (in other words, all of A through Z has been used), the project team can then choose to use a combination of letters and numbers (such as A-1, B-1, etc.), or the project team can begin using double letters for the next 26 (AA, BB, etc.), triple letters for the next 26 (AAA, BBB, etc.).’
This term is defined in the 3rd and the 4th edition of the PMBOK.