The maximum amount that a worker can elect to contribute to a 401(k) retirement plan was $17,500 in 2014 and $18,000 as of 2015, according to the Internal Revenue Service. The amount is often increased from one year to the next to address cost-of-living adjustments.
The $18,000 limit is an aggregate limit across all elective deferral plans in which a worker may participate, reports the Internal Revenue Service. People who are 50 or older do have the option to contribute an additional $6,000 to a traditional retirement plan as of 2015. This additional election is known as a "catch-up contribution."