In the United States, a 401(k) plan is the tax-qualified, defined-contribution pension account defined in subsection 401(k) of the Internal Revenue Code.
Under the plan, retirement savings contributions are provided (and sometimes proportionately matched) by an employer, deducted from the employee’s paycheck before taxation (therefore tax-deferred until withdrawn after retirement or as otherwise permitted by applicable law), and limited to a maximum pre-tax annual contribution of $18,000 (as of 2015).
Other employer-provided defined-contribution plans include 403(b) plans, for nonprofit institutions, and 457(b) plans for governmental employers.
These plans are all established under section 401(a) of the Internal Revenue Code. 401(a) plans may provide a total annual addition of $52,000 (as of 2014) per plan participant, including employee and employer contributions.