[Updated with 2015 changes] I recently received a few questions regarding 401k retirement plans and contribution limits. The first thing to understand is that there are two main types of contributions that go into these plans. One is your contribution, or elective deferral, and the other is your employers, or matching, contribution. Secondly there are four annual contribution limits you need to be aware of : Your employee contribution (elective deferral or 402g) limit, catch-up contribution limits (for those over 50), employer contribution (415) limits and maximum annual contribution limits.
Per the table below the maximum employee (elective deferral) annual contribution limit across all 401k plans will rise to $18,000 (vs. $17,500 in 2014). The maximum annual contribution is $53,000 (in 2014 it was $52,000), which includes elective deferrals, employer matching and discretionary contributions, but excludes catch-up contributions for those over 50 (see below). In addition, the amount of employee compensation (especially for higher income earners) that can be taken into account when determining employer and employee contributions was $245,000 for 2011 and $250,000 for 2012.
Maximum Employer contribution limits. Matching 401K or 403b contributions made by your employer are not counted towards your annual contribution limit or 100% of your salary, whichever is the smaller amount. But do count towards the maximum annual contribution limit that includes employee and employer contributions. Though most employers rarely give anywhere near the maximum, most generally match 3% to 6% of employee contributions.
Catch-up contributions. If you are age 50 or over at the end of the calendar year, you are permitted to make additional, “catch-up”, elective deferral contributions. These catch-up contributions are not subject to the annual general limits that apply to 401k plans. The catch-up contribution you can make for a year cannot exceed the lesser of the annual catch-up contribution limit, or the excess of your compensation over the elective deferrals that are not catch-up contributions.