Which of the following is NOT a base definition of 415 compensation?

The correct answer highlights that discretionary bonuses are not considered a base definition of 415 compensation. In the context of 401(k) plans and the Internal Revenue Code, 415 compensation typically refers to compensation taken into account for determining contribution limits. The base definitions of 415 compensation include W-2 compensation, includable compensation, and wages for income tax withholding, all of which are specified in various regulations and are designed to establish a clear measure of an employee's earnings for purposes of retirement plan contributions.

Discretionary bonuses, while they may be part of an employee's overall earnings, are not included in 415 compensation because they do not have a uniform application across all employees and can vary significantly based on employer decisions. This exclusion helps maintain consistency and fairness in the calculation of contributions and ensures that the limits imposed under Section 415 are applied accurately and equitably.