A 401 (k) contribution is a savings account in the United States. that allows individuals to save for their retirement. Individuals can start to withdraw these funds after they reach 59-1/2 years of age. Restrictions may apply before that age. These types of plans were first widely adopted as savings retirement plans for workers in the U.S. at the beginning of 1980s. 401 (k) surfaced as a marginal to the traditional retirement pension that was paid by employers. Employer contributions to 401 (k) can vary, but overall the 401K was effective in shifting the burden for retirement accounts as well as savings to the workers themselves.