W2 Box 12a Code E - Number Doesn't Match My 403b Contributions

Just got my W2 for the year and I'm a bit confused about box 12a with the code E. From what I understand, this should show my 403b contributions for the tax year. The problem is that the number listed there doesn't match what I've been keeping track of all year for my 403b contributions. After doing some math and checking my pay stubs, I think I figured it out - the number in box 12a E seems to be my total voluntary 403b contributions but doesn't include the mandatory contributions my employer requires me to make. I work for a large healthcare system so I assume they're doing the W2 correctly, but I want to make sure I understand this properly. Are mandatory 403b contributions handled differently on the W2? Is it normal that box 12a only shows voluntary contributions and not the mandatory ones? Does the company account for the mandatory contributions elsewhere in the taxes they withhold?

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18 comments

Esteban Tate

•8M

The W2 box 12a with code E specifically shows your elective deferrals to a 403b retirement plan. "Elective" is the key word here - these are the voluntary contributions you chose to make, not the mandatory ones your employer requires. Mandatory contributions are treated differently for tax purposes. They're considered "non-elective" contributions and aren't reported in box 12a with code E. Your employer is filling out your W2 correctly based on what you've described. The mandatory contributions are still pre-tax in most cases, but they're accounted for differently because you didn't have a choice about making them - they were a condition of your employment. Your employer has already adjusted your taxable wages accordingly.

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Esteban Tate

•8M

That's exactly right! Both your mandatory and voluntary contributions to your 403b should be reducing the taxable wages shown in Box 1 of your W2. Only the voluntary (elective) deferrals are reported separately with code E in Box 12a. This reporting method allows the IRS to verify you haven't exceeded the annual elective deferral limits, which only apply to the voluntary portion of your contributions. The mandatory contributions are still pre-tax but follow different rules.

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Ivanna St. Pierre

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Atticus Domingo

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I actually tried the taxr.ai service after commenting here, and I have to admit I was wrong to be skeptical. I uploaded my W2 with all these confusing retirement codes (I have both voluntary and mandatory contributions too), and it broke everything down clearly. It explained exactly why my Box 12a code E didn't match my total contributions and identified the mandatory portion that wasn't included there. It even showed me where to look on my last pay stub to verify everything. Super helpful for understanding these technical tax form details without having to wade through IRS publications!

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Kingston Bellamy

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I need to eat my words from my previous comment. After getting nowhere with the IRS for weeks about my retirement contribution questions, I tried the Claimyr service. Within 27 minutes I was speaking with an actual IRS agent who clarified everything about my W2 code E reporting. They confirmed what others here said - Box 12a with code E only shows voluntary deferrals, not mandatory contributions. The agent also helped me understand how to verify that my employer reported everything correctly by checking my last pay stub against my W2. Completely worth it to finally get a definitive answer from the source!

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Joy Olmedo

•8M

You should check your year-end pay stub and compare it with your W2. Your last pay stub of the year should have a YTD (year-to-date) total for all your 403b contributions - both mandatory and voluntary. Then compare: 1. The Box 1 wages on your W2 should be lower than your gross income by at least the amount of BOTH types of contributions 2. Box 12a code E should match ONLY your voluntary contributions 3. There should be no specific box showing your mandatory contributions If these three things check out, your W2 is correct!

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Joy Olmedo

•8M

The easiest way to identify them is by looking at the names or codes on your pay stub. Elective (voluntary) deferrals are usually labeled something like "403b," "403b elective," or "voluntary retirement." The mandatory contributions might be labeled "mandatory retirement," "required contribution," or sometimes with your employer's specific plan name. Another clue is that elective deferrals usually show a percentage or amount that matches what you selected during benefits enrollment. Mandatory contributions are typically a fixed percentage that's the same for all employees. If you're still unsure, your HR or benefits department can tell you exactly which line items are which type of contribution.

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Kiara Greene

•8M

I'm a benefits coordinator (not tax advice!) and just wanted to add that different employers handle 403b reporting slightly differently. If you work in education or healthcare, there's a good chance you have both mandatory and voluntary contributions. The 403b contribution limits ($23,000 for 2025 for those under 50) only apply to voluntary contributions (those shown in Box 12a with code E). Mandatory contributions don't count toward this limit, which is actually advantageous!

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