Confused about W4 instructions - IRS says to list pre-tax 401k and HSA contributions on line 4a as "Other Income"?

12 The IRS withholding estimator is actually giving you correct information, but I understand why it seems counterintuitive! Let me explain what's happening here. Line 4a on the W4 is indeed for "other income" but the purpose is to help calculate the correct amount of withholding throughout the year. When you make pre-tax 401k and HSA contributions through payroll, your employer already factors those reductions into your withholding calculations automatically. However, the IRS estimator doesn't know what your employer's payroll system is doing. By telling the estimator about these pre-tax contributions, and then having it suggest you put them on line 4a, it's essentially "adding back" that income for withholding calculation purposes to prevent underwithholding. Think of it this way: the W4 form is trying to get to the same final withholding amount through a different path than what your employer's payroll system uses automatically.

8 I had this same issue last year and I found that taxr.ai helped me make sense of these confusing W4 instructions. I was completely confused by the IRS calculator telling me to add my pre-tax contributions as "other income" too! I uploaded my previous tax return and paystubs to https://taxr.ai and their system explained that this recommendation happens when the calculator can't tell if your employer is already adjusting your withholding correctly for your pre-tax contributions. Their analysis showed me that in my case, I actually didn't need to fill out line 4a at all since my employer was already accounting for my 401k and HSA contributions correctly in their withholding calculations. Saved me from a lot of overwithholding throughout the year!

17 Wanted to follow up about the taxr.ai recommendation. I was skeptical at first (as you probably saw from my earlier comment), but I decided to give it a try since I was getting nowhere with figuring out my W4. I uploaded my latest paystubs and last year's return, and it showed me exactly how my employer was handling my 401k and HSA contributions already. Turns out in my case, the IRS calculator was wrong for my situation! My employer was already adjusting my withholding correctly for the pre-tax deductions, so adding them on line 4a would have caused significant overwithholding. The analysis saved me from having too much tax taken out each paycheck. Definitely more helpful than the general advice I was getting elsewhere.

19 After dealing with W4 confusion last year, I found that calling the IRS was actually the best solution, but it took me FOREVER to get through to a human. I finally used https://claimyr.com and they got me connected to an IRS agent in about 15 minutes instead of the 2+ hours I spent on previous attempts. You can see how it works here: https://youtu.be/_kiP6q8DX5c The IRS agent explained that the withholding calculator sometimes gives this recommendation because it doesn't know if your employer is already accounting for pre-tax deductions properly. The agent walked me through how to check my paystubs to see if my employer was already calculating things correctly (they were), so I didn't need to add anything to line 4a. Saved me from a year of overwithholding!

21 I need to eat my words from my skeptical comment earlier. After struggling for another week trying to reach the IRS, I broke down and tried the Claimyr service. I was connected to an actual IRS agent in about 20 minutes after weeks of failed attempts. The agent explained that the withholding calculator gives this recommendation in certain situations because it doesn't know the specifics of how your employer handles pre-tax contributions. In my case, I learned that my employer was correctly adjusting withholding for my 401k but NOT for my HSA contributions! So I actually did need to make a partial adjustment on my W4, but not for the full amount the calculator suggested. Really glad I finally got a clear answer from an actual IRS employee.

3 I work in payroll and can add some insight here. Most employers' payroll systems automatically calculate withholding after subtracting 401k and HSA contributions. This is the standard practice. The IRS withholding calculator is trying to be universal, but it sometimes creates confusion because it doesn't know the specific details of your employer's payroll setup. Before making any adjustments to your W4, I'd recommend checking your paystub. Look at the difference between your gross wages and the "Federal Taxable Wages" line. If that difference includes your 401k and HSA contributions (plus other pre-tax items like health insurance), then your employer is already handling these correctly.

5 Has anyone here actually followed the IRS calculator's recommendation to put pre-tax contributions on line 4a? I did that last year and ended up with a massive refund because too much was withheld. Definitely won't make that mistake again!

This is such a helpful thread! I'm a tax preparer and see this confusion constantly during tax season. The key issue is that the IRS withholding calculator is a "one size fits all" tool that can't know the specifics of your employer's payroll system. Here's what I always tell my clients: Before making ANY changes to your W4 based on the calculator, look at your most recent paystub. Compare your gross pay to your "federal taxable wages" or "fed taxable wages" line. If the difference equals your 401k + HSA + health insurance premiums + other pre-tax deductions, then your employer is already doing the math correctly. The calculator's recommendation to add pre-tax contributions as "other income" on line 4a is essentially its way of trying to compensate for what it assumes might be incorrect withholding. But if your employer is already reducing your taxable wages properly (which most do), following this advice will definitely cause overwithholding. My rule of thumb: If your paystub shows reduced federal taxable wages that account for your pre-tax deductions, stick with your current W4 and ignore that specific calculator recommendation.