To tell if your 401(k) is Roth or traditional, look in three places: the deduction line on your pay stub, Box 12 on your W-2, and the contribution-source breakdown inside your retirement plan’s online portal. A Roth contribution is labeled with the word “Roth” somewhere; a traditional contribution is labeled “Pre-Tax” or just “401k.” If none of your documents show the word “Roth,” your contributions are almost certainly traditional pre-tax.
Start With Your Pay Stub
The deductions section of your pay stub is the quickest place to check. Roth 401(k) deductions typically appear as “Roth 401k,” “Employee Roth,” “Roth Deferral,” or “R401K.” Traditional contributions show up as “401k,” “Pre-Tax,” or “Pre-Tax Deferral.” A generic “401(k)” line with no Roth indicator almost always means traditional pre-tax.
You can confirm the type by watching how the contribution affects your taxable wages. Roth money is withheld after tax, so your federal income tax is calculated on your full gross pay before the Roth deduction comes out. Traditional contributions reduce taxable income first, lowering the income tax withheld for the same dollar amount. A $500 Roth contribution leaves you with a smaller paycheck than a $500 traditional contribution, because you paid tax on that $500 before it went into the account. If your tax withholding doesn’t move when your contribution amount changes, the money is going in pre-tax.
Roth Is Not the Same as Voluntary After-Tax
Some plans offer a third option that’s easy to mistake for Roth: voluntary after-tax contributions. Both come out of your paycheck after taxes, but the tax treatment at withdrawal is different. Qualified Roth distributions are entirely tax-free, including earnings. Voluntary after-tax distributions only let you take back your original contributions tax-free; you still owe income tax on any earnings.
On a pay stub, voluntary after-tax money often appears as “After-Tax,” “Post-Tax,” or “Employee After-Tax,” without the word “Roth.” If you see an after-tax label without “Roth,” ask your plan administrator which type it is before assuming you have a Roth balance.
Check Box 12 of Your W-2
Your year-end Form W-2 is the most authoritative payroll document, because the IRS uses it to verify contributions. Box 12 carries letter codes identifying the exact type of retirement deduction. For a 401(k), two codes matter:
- Code D: traditional pre-tax 401(k) contributions.
- Code AA: designated Roth contributions under a 401(k) plan.
Code D alone means everything went in pre-tax. Code AA alone means everything went in as Roth. Both codes appearing means you split your contributions during the year, and the dollar amount next to each shows exactly how much went into each bucket.1Internal Revenue Service. Common Errors on Form W-2 Codes for Retirement Plans
If you’re in a 403(b) or governmental 457(b) instead of a 401(k), the Roth codes differ: Code BB for Roth 403(b) contributions and Code EE for Roth governmental 457(b) contributions. The principle is the same: the code identifies the tax treatment.1Internal Revenue Service. Common Errors on Form W-2 Codes for Retirement Plans
Look at Your Plan Portal
Your plan’s online portal shows a running view of balances by tax type. Most providers label each pool by contribution source, so you may see separate lines for “Employee Pre-Tax,” “Roth Deferral,” and “Employer Match.” Separate Roth and traditional balances mean you’ve split contributions or changed elections at some point. A single balance with no tax-type breakdown usually means the account is entirely traditional.
Quarterly and annual statements carry the same breakdown. The transaction history is especially useful because each deposit is tagged with the tax designation it was assigned at payroll transfer, so you can pinpoint when contributions shifted from one type to the other.
One note on the employer match. Matching contributions have historically gone into a pre-tax account regardless of whether your own contributions are Roth. Under the SECURE 2.0 Act, plans can now let employees designate employer matching or nonelective contributions as Roth, and those Roth employer contributions appear on a Form 1099-R for the year they’re allocated rather than on your W-2.2Internal Revenue Service. SECURE 2.0 Act Changes Affect How Businesses Complete Forms W-2 A “Roth Employer Match” line in your portal means your plan has adopted this option and you elected into it.
Read the Summary Plan Description
Every employer-sponsored retirement plan must give participants a Summary Plan Description (SPD), written in language an average participant can understand.3Office of the Law Revision Counsel. 29 USC 1022 – Summary Plan Description The SPD tells you whether your employer even offers a Roth option. If the plan hasn’t adopted a qualified Roth contribution program, Roth contributions aren’t available regardless of what you think you elected.4Office of the Law Revision Counsel. 26 USC 402A – Optional Treatment of Elective Deferrals as Roth Contributions
Look for a section titled something like “Employee Contributions” or “Types of Deferrals.” If Roth is allowed, that section describes the election process and any restrictions. You can request the SPD from HR or the plan administrator, who must furnish it within 30 days of a written request.
Ask Your Plan Administrator
When the documents leave you uncertain, call or email the plan administrator or HR directly. Have your employee ID and recent contribution dates handy. Ask for your “elective deferral tax status” and request written confirmation. This step also verifies that what payroll reports matches what the brokerage actually received. Mismatches happen.
Fixing a Misclassified Contribution
If your employer coded a Roth contribution as traditional, or the other way around, the IRS has a defined correction process. When an intended Roth contribution was treated as pre-tax, the fix is to transfer the deferrals plus earnings from the pre-tax account into the Roth account. The employer then issues a corrected W-2 for the year of the error, or includes the transferred amount in your compensation for the year of correction. A pre-tax election that was mistakenly deposited as Roth is corrected the other way, again with a corrected W-2.5Internal Revenue Service. Fixing Common Mistakes – Correcting a Roth Contribution Failure
The sooner you spot the error, the simpler the fix. Checking your pay stub each pay period rather than waiting for the W-2 saves you from months of misallocated contributions and amended tax returns.
Why Knowing the Difference Matters
The Roth versus traditional label determines how much tax you’ll owe decades from now when you withdraw the money. Qualified distributions from a Roth 401(k) are excluded from gross income, meaning zero federal income tax on both contributions and earnings. Traditional 401(k) withdrawals are taxed as ordinary income because you never paid tax on the money going in. A Roth withdrawal only qualifies as tax-free if you’re at least 59½ (or qualify through disability or death) and at least five tax years have passed since your first Roth contribution to the plan.6Office of the Law Revision Counsel. 26 USC 402A – Optional Treatment of Elective Deferrals as Roth Contributions
Traditional and Roth contributions share a single annual cap. For 2026, that limit is $24,500. Workers 50 and older can add $8,000 in catch-up contributions for a total of $32,500.7Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500 A SECURE 2.0 provision gives an even higher catch-up limit of $11,250 to participants who turn 60, 61, 62, or 63 during the year, allowing them to defer up to $35,750.8Internal Revenue Service. IRS Notice 2025-67 – 2026 Amounts Relating to Retirement Plans and IRAs Splitting contributions between Roth and traditional doesn’t raise the cap; the combined total across both types cannot exceed these limits.
Two SECURE 2.0 changes raise the stakes. Starting in 2024, Roth 401(k) accounts are no longer subject to required minimum distributions during the account holder’s lifetime, while traditional 401(k) accounts still force withdrawals starting at age 73. And for tax years after December 31, 2026, employees whose prior-year wages exceed a certain threshold will be required to make catch-up contributions as Roth rather than traditional. The IRS has issued final regulations on this rule, though the practical impact starts with the 2027 tax year.9Internal Revenue Service. Treasury, IRS Issue Final Regulations on New Roth Catch-Up Rule, Other SECURE 2.0 Act Provisions For higher earners over 50, the plan will eventually route catch-up dollars into a Roth account whether or not you prefer that outcome, which is one more reason to confirm today how your contributions are classified.