The total dollar amount contributed in a given year to a participant’s retirement account under a defined-contribution plan. An annual addition is the sum of employer contributions, employee contributions and forfeitures in a particular year. The annual addition is subject to a maximum limit. This annual addition limit is the lesser of 100% of the participant’s compensation for the year or the dollar limit in effect for the year. The annual addition dollar limit was fixed at $49,000 for each year from 2009 to 2011.
Further explanation: Certain amounts credited to a participant’s plan are not considered as annual additions. These include “catch-up” contributions, rollover contributions and loan repayments. In addition, employee contributions transferred from a qualified plan to a defined contribution plan do not count towards the annual addition.
Definition courtesy of Investopedia