The Internal Revenue Service has announced the 2018 limits that affect the operation of tax-qualified retirement plans, including 401(k) plans, and certain other types of employee benefit plans, including deferred compensation plans that may be subject to Internal Revenue Code §409A. The amount by which the limits are adjusted each year is based on a cost of living index. Not all limits increase every year.
The Social Security (OASDI) taxable wage base, which governs the amount of pay subject to Social Security tax withholding and affects plans that are "integrated" with Social Security, also is subject to adjustment annually. For 2018, the OASDI taxable wage base has been increased to $128,700.