Most employees are familiar with the option of contributing pre-tax dollars to a traditional 401(k) plan. These contributions reduce taxable income today while allowing investments to grow on a tax-deferred basis until retirement.
If your employer’s plan includes a Roth 401(k), you may also have the option to make after-tax contributions that can potentially be withdrawn tax-free in retirement. However, some plans offer a lesser-known third option: non-Roth after-tax 401(k) contributions.
Understanding how this strategy works can help you determine whether it’s a valuable addition to your retirement savings plan.
Traditional vs. Roth 401(k) Contributions
For 2026, employees can generally contribute up to $24,500 to a 401(k) plan through elective salary deferrals.
Workers age 50 and older may qualify for additional catch-up contributions. The 2026 catch-up limit is either $8,000 or $11,250, depending on age. Employees whose 2025 compensation exceeded $150,000 must make catch-up contributions to a Roth 401(k) account.
Traditional 401(k) contributions are made with pre-tax dollars. While these contributions are still subject to Social Security and Medicare taxes (FICA taxes), they reduce taxable income for federal income tax purposes. Investments grow tax-deferred, and withdrawals in retirement are generally taxed as ordinary income.
Roth 401(k) contributions work differently. Contributions are made with after-tax dollars and do not reduce current taxable income. However, earnings can grow tax-free, and qualified withdrawals may be entirely tax-free if certain requirements are met. Generally, qualified distributions occur after age 59½ and after the account has been open for at least five years.
How Non-Roth After-Tax Contributions Work
Non-Roth after-tax 401(k) contributions are separate from both traditional and Roth contributions.
Because these contributions are made with money that has already been taxed, they are included in your taxable wages and are subject to federal income tax, FICA taxes, and potentially state and local income taxes.
Unlike Roth contributions, however, these funds are deposited into a traditional 401(k) account rather than a Roth account. As a result, they do not receive the same tax-free growth and withdrawal benefits associated with Roth accounts.
So why would someone choose this option?
The primary advantage is the ability to save more money for retirement after reaching the standard elective deferral limit.
A Way to Increase Retirement Savings
Once you’ve reached the annual elective deferral limit, after-tax contributions may allow you to continue adding funds to your 401(k).
While these contributions do not provide an immediate tax deduction, any investment earnings grow tax-deferred until withdrawn. This can make them an attractive option for individuals looking to maximize retirement savings.
Keep in mind that total annual additions to a 401(k) plan are still capped.
For 2026, the combined total of:
- Employee elective deferrals (excluding catch-up contributions)
- Employer matching or profit-sharing contributions
- Employee after-tax contributions
cannot exceed the lesser of:
- $72,000, or
- 100% of compensation
Understanding Tax Basis
One important feature of after-tax contributions is that they create tax basis within your account.
This means the amount you contributed after taxes have already been paid can eventually be withdrawn without being taxed again.
However, any investment gains generated by those contributions will generally be taxable when withdrawn.
This is a key distinction from Roth 401(k) accounts, where qualified withdrawals of both contributions and earnings can be tax-free.
Example of After-Tax 401(k) Contributions
Consider the following scenario:
- Your annual salary in 2026 is $150,000.
- You are under age 50.
- Your employer offers a 50% matching contribution.
- The plan allows after-tax contributions.
You contribute the maximum elective deferral amount of $24,500 to your traditional 401(k).
Your employer contributes a matching amount of $12,250.
Since the total annual contribution limit is $72,000, you could still contribute up to $35,250 in after-tax contributions:
$72,000 − $24,500 − $12,250 = $35,250
Suppose you choose to contribute an additional $10,000 after tax.
In this situation:
- Your $24,500 traditional 401(k) contribution reduces your taxable income for federal income tax purposes but remains subject to FICA taxes.
- Your employer’s $12,250 matching contribution is not subject to federal income tax or FICA taxes when contributed.
- Your $10,000 after-tax contribution is included in taxable income and subject to income and payroll taxes, but it establishes a $10,000 tax basis that can later be withdrawn tax-free.
Keep Nondiscrimination Rules in Mind
Employer-sponsored retirement plans must comply with federal nondiscrimination rules designed to ensure benefits are not disproportionately favoring highly compensated employees.
In most situations, these rules do not prevent employees from making after-tax contributions. However, certain circumstances could affect contribution opportunities depending on the structure and participation levels within a company’s retirement plan.
Reviewing your plan’s specific provisions can help avoid surprises.
Is This Strategy Right for You?
If you’re already contributing the maximum allowed through standard 401(k) deferrals, after-tax contributions may provide an effective way to increase retirement savings and take advantage of continued tax-deferred growth.
The strategy is especially attractive for higher-income individuals who want to save beyond traditional contribution limits.
Because retirement plans and tax rules can be complex, it’s important to evaluate how after-tax contributions fit into your overall financial strategy before making a decision.
Final Thoughts
After-tax 401(k) contributions are often overlooked, but they can offer an additional opportunity to build retirement wealth once regular contribution limits have been reached. While they don’t provide the same tax advantages as Roth accounts, they can still help boost long-term savings and create additional flexibility for retirement planning.
Before moving forward, consider consulting a financial or tax professional to determine whether this strategy aligns with your retirement goals and tax situation.