The limit on employee contributions to 401(k) plans for 2015 is $18,000, according to the IRS. In addition, employees over age 50 are allowed to make catch-up contributions of up to $6,000. The same limits apply to 403(b) and 457 plans.
The limits on contributions and on catch-up contributions are each $500 higher than in tax year 2014, notes the IRS. The IRS announces changes in contribution limits when the cost-of-living index changes. The index triggers other regulatory changes as well, such as income eligibility levels or changes to tax credits. A tax professional is able to advise regarding the specifics of a tax situation.