The 401(k) contribution limit for 2018 rose to $18,500, a $500 increase over the 2017 limit. This was one of only two retirement plan contribution limits that changed for the year, as low inflation kept most other thresholds frozen. Whether you are maximizing your retirement savings or just getting started, understanding these limits helps you plan contributions strategically and avoid costly penalties.
Retirement plan contribution limits are adjusted annually by the IRS based on inflation. In years when inflation stays low, many limits carry forward unchanged. For 2018, that pattern held across most plan types, but the 401(k) increase offered a meaningful opportunity for savers to shelter more income from taxes.
2018 retirement plan contribution limits at a glance
The IRS publishes retirement plan contribution limits each fall for the following tax year. Here is a complete breakdown of the 2018 limits across all major plan types:
| Type of Limit | 2018 Limit |
| — | — |
| Elective deferrals to 401(k), 403(b), 457(b)(2), and 457(c)(1) plans | $18,500 |
| Contributions to defined contribution plans | $55,000 |
| Contributions to SIMPLEs | $12,500 |
| Contributions to IRAs | $5,500 |
| Catch-up contributions to 401(k), 403(b), 457(b)(2), and 457(c)(1) plans | $6,000 |
| Catch-up contributions to SIMPLEs | $3,000 |
| Catch-up contributions to IRAs | $1,000 |
Only two limits increased from 2017: the 401(k) elective deferral limit (up $500 to $18,500) and the defined contribution plan limit (up $1,000 to $55,000). Every other threshold remained unchanged.
Why the 401(k) limit increased while most others stayed flat
The IRS adjusts retirement plan contribution limits using cost-of-living adjustments (COLAs) tied to the Consumer Price Index. Each limit has a different rounding increment, which means small changes in inflation can push one limit up while leaving others untouched.
For 2018, inflation was just high enough to trigger the $500 increment for 401(k) elective deferrals and the $1,000 increment for the overall defined contribution plan limit. The IRA contribution limit, SIMPLE plan limit, and all catch-up contribution amounts remained at their 2017 levels because inflation did not cross their respective rounding thresholds.
This pattern is common in low-inflation environments. Savers should not assume that every limit rises each year. Instead, checking the IRS announcement each October (typically released in IRS Notice 2017-64 for 2018 limits) ensures you set the right contribution amount before the new year begins.
How to maximize your 401(k) contributions in 2018
The $18,500 elective deferral limit applied to the total of your pre-tax and designated Roth contributions to all 401(k), 403(b), and governmental 457(b) plans combined. If you participated in more than one plan during the year, your combined contributions across all plans could not exceed this amount.
To reach the maximum, divide $18,500 by the number of pay periods remaining in the year and adjust your deferral percentage accordingly. Many plan administrators allowed dollar-amount elections rather than percentage-based ones, which made it easier to hit the exact limit without over- or under-contributing.
Employer-sponsored plans are governed by detailed IRS 401(k) plan rules in addition to the annual contribution limits, so plan documents may impose their own constraints. If your employer offered a matching contribution, your own elective deferrals plus the employer match could not exceed the $55,000 defined contribution limit (or $61,000 with catch-up contributions for participants age 50 and older). Employer matches did not count against your $18,500 personal limit, making them essentially free money on top of your own savings.
Catch-up contributions for participants age 50 and older
The catch-up contribution for 401(k) plans remained at $6,000 for 2018. This provision allowed participants who turned 50 by December 31, 2018, to contribute up to $24,500 total ($18,500 regular deferral plus $6,000 catch-up). Catch-up contributions are a critical tool for workers who started saving later in their careers or who want to accelerate their retirement savings as they approach retirement age.
SIMPLE plan participants age 50 and older could contribute an additional $3,000 above the standard $12,500 limit, bringing their total to $15,500. IRA catch-up contributions held steady at $1,000 for participants age 50 and older, raising the total IRA contribution limit to $6,500.
These catch-up amounts are set by statute for IRAs ($1,000 is fixed and not indexed for inflation) and by COLA adjustments for 401(k) and SIMPLE plans. The 401(k) catch-up limit had not increased since 2015, reflecting the same low-inflation dynamics that kept other limits flat.
IRA contribution limits for 2018
The IRA contribution limit for 2018 remained at $5,500 ($6,500 for those age 50 and older). This limit applied to the combined total of contributions to all traditional and Roth IRAs. Contributing $3,000 to a traditional IRA, for example, left only $2,500 available for Roth IRA contributions.
Income-based limits further restricted certain IRA contributions. For 2018, the ability to deduct traditional IRA contributions began phasing out at $63,000 of modified adjusted gross income (MAGI) for single filers covered by a workplace plan, and at $101,000 for married couples filing jointly when the contributing spouse had a workplace plan.
Roth IRA contribution eligibility also phased out at higher income levels. Single filers with MAGI between $120,000 and $135,000 could make only partial Roth contributions, and contributions were fully phased out above $135,000. For married couples filing jointly, the phase-out range was $189,000 to $199,000.
These income thresholds did increase slightly for 2018, giving some higher-income taxpayers renewed access to deductible IRA contributions or Roth contributions who had been phased out in prior years.
Tax reform and its impact on retirement plan contributions
Higher-income taxpayers received welcome news when the Tax Cuts and Jobs Act, signed into law in December 2017, preserved the pre-tax treatment of 401(k) contributions. Earlier versions of the tax reform legislation had proposed capping pre-tax 401(k) contributions at $2,400 and requiring the remainder to be made as after-tax Roth contributions. That provision was removed from the final bill.
The preservation of pre-tax contribution limits meant that workers could continue to reduce their current taxable income by up to $18,500 (or $24,500 with catch-up contributions) through traditional 401(k) deferrals. For high earners in the top tax brackets, this represented significant tax savings in the contribution year, with taxes deferred until withdrawals in retirement.
However, the new tax law did make other changes that indirectly affected retirement planning, including lower marginal tax rates that reduced the immediate tax benefit of pre-tax contributions and changes to itemized deductions that shifted some taxpayers’ overall tax strategies. These factors made it worth revisiting whether pre-tax or Roth contributions offered the better long-term outcome for each individual’s situation. A review with a qualified advisor through dedicated tax advisory services can help align deferral elections with your broader tax picture.
Other factors that may limit your contributions
Beyond the IRS-published limits, several additional rules could reduce how much you were allowed to contribute to retirement plans in 2018. Highly compensated employees (those earning more than $120,000 in the prior year) faced potential restrictions under nondiscrimination testing rules. If a plan’s rank-and-file employees contributed at low rates, the plan might have had to limit or refund contributions from highly compensated participants.
The annual compensation limit for calculating employer contributions and determining benefit accruals was $275,000 for 2018. Earnings above this threshold were disregarded for plan purposes, which could reduce the employer match for executives and other high earners.
Self-employed individuals had their own set of considerations. Solo 401(k) plans allowed both employee deferrals (up to $18,500) and employer profit-sharing contributions (up to 25% of net self-employment income), subject to the $55,000 combined limit. Calculating the correct maximum required factoring in the self-employment tax deduction, which reduced the effective compensation base. Business owners weighing plan design alongside entity-level tax planning often benefit from coordinated accounting services that keep payroll, retirement, and tax filings aligned.
Frequently Asked Questions
What was the 401(k) contribution limit for 2018?
The 401(k) contribution limit for 2018 was $18,500 for elective deferrals, a $500 increase from the 2017 limit of $18,000. This limit applied to 401(k), 403(b), and most 457 plans. Participants age 50 and older could contribute an additional $6,000 in catch-up contributions, bringing their total to $24,500.
How much could you contribute to an IRA in 2018?
The IRA contribution limit for 2018 was $5,500, or $6,500 for individuals age 50 and older. This limit applied to the combined total of all traditional and Roth IRA contributions. Income-based phase-outs could reduce or eliminate your ability to make deductible traditional IRA contributions or any Roth IRA contributions.
What is a catch-up contribution and who qualifies?
A catch-up contribution is an additional amount that retirement plan participants age 50 and older can contribute above the standard limit. For 2018, the catch-up contribution was $6,000 for 401(k) plans, $3,000 for SIMPLE plans, and $1,000 for IRAs. You qualified if you turned 50 at any point during the calendar year.
Did tax reform change 401(k) contribution limits?
No. The Tax Cuts and Jobs Act of 2017 preserved the pre-tax treatment of 401(k) contributions at the full $18,500 limit. Earlier proposals to cap pre-tax contributions at $2,400 were removed from the final legislation. Retirement plan contribution limits continued to be set by IRS cost-of-living adjustments, not the tax reform bill.
Can you contribute to both a 401(k) and an IRA?
Yes, you can contribute to both a 401(k) and an IRA in the same year. However, your ability to deduct traditional IRA contributions may be limited if you or your spouse are covered by a workplace retirement plan and your income exceeds certain thresholds. Roth IRA contributions are also subject to income-based phase-outs regardless of workplace plan participation.
Why do some retirement plan limits stay the same each year?
Retirement plan contribution limits are indexed to inflation using IRS cost-of-living adjustments. Each limit has a specific rounding increment. For example, the 401(k) limit adjusts in $500 increments. When inflation is low, it may not be enough to trigger the next increment for every limit, which is why some limits increase while others remain flat from year to year.
