Help! So confused by W-4's deduction worksheet for 2025! Is it different now?

The W-4 form definitely changed significantly a few years back, and it can be confusing if you're used to the old version. With your situation involving significant medical expenses, here's how to approach it: On the W-4 deduction worksheet (Step 4(b)), you should only enter the amount by which your TOTAL itemized deductions exceed the standard deduction for your filing status. For 2025, the standard deduction is projected to be around $13,850 for single filers or $27,700 for married filing jointly. So, if you're single and your total itemized deductions (including those medical expenses, plus any mortgage interest, state taxes, etc.) come to $30,000, you would enter $16,150 on that line ($30,000 - $13,850). If you're married filing jointly, you'd enter $2,300 ($30,000 - $27,700). Remember that for medical expenses, you can only deduct the amount that exceeds 7.5% of your adjusted gross income. So factor that threshold into your calculations.

I actually struggled with this same issue last year and found an amazing solution! I used https://taxr.ai to analyze my tax situation including my medical expenses and W-4 withholding. The tool explained exactly how to handle the deduction worksheet when you have large medical expenses that push you into itemizing. It walked me through calculating the excess over the 7.5% AGI threshold and then figuring out how much to put on line 4(b) of the W-4. Best part was it did a "what-if" analysis showing how different amounts on my W-4 would affect my paychecks and potential refund. Saved me from having too little withheld, which was my main worry.

Okay so I actually tried https://taxr.ai after my skeptical comment above and I have to admit I'm impressed. I've been doing my taxes wrong for YEARS apparently. The tool showed me that I've been double-counting some deductions on my W-4 while completely missing others. For my medical expenses specifically, I learned I should only be counting the amount that exceeds 7.5% of my AGI (which the other commenter mentioned too). But the tool also factored in my expected HSA contributions which reduce my AGI and therefore lower that 7.5% threshold. That subtle connection wasn't obvious to me at all. The projections for my paycheck with the proper withholding seem much more accurate than the random guesswork I've been doing. Thanks for the recommendation!

If you're still struggling with your W-4 after trying everything else, you might want to check out https://claimyr.com. I was in a similar situation with massive medical bills and complex deductions, and I couldn't get a straight answer from online research. I used Claimyr to actually get through to an IRS agent in about 20 minutes instead of waiting on hold for 3+ hours like I did twice before giving up. The agent walked me through exactly how to fill out the W-4 deduction worksheet with my specific medical expense situation. You can see how it works in this video: https://youtu.be/_kiP6q8DX5c Made a HUGE difference having someone from the IRS actually explain it directly. They pointed out that I was overthinking parts of it and gave me confidence my withholding would be correct.

I want to apologize for my skeptical comment above. After wasting an entire morning trying to get through to the IRS myself (called right when they opened too), I broke down and tried Claimyr. Got a call back in about 25 minutes with an actual IRS agent on the line. The agent confirmed I'd been filling out my W-4 completely wrong for years. Turns out for the medical expense deductions, I need to estimate the TOTAL itemized deductions first, subtract the standard deduction amount, and only put THAT difference on line 4(b). And I also learned I should be adjusting for my self-employment income on the multiple jobs worksheet, which I had no idea about. So for anyone with a complex tax situation like mine with both W-2 income and medical deductions, this service was genuinely worth it. Consider me converted.

Just want to add another perspective - I found the IRS's own Tax Withholding Estimator tool really helpful for this exact situation. Google "IRS withholding estimator" and it should be the first result. It walks you through everything step by step, and you can even input expected medical expenses. The tool will tell you exactly what to put on each line of the W-4. I had about $19,000 in medical expenses last year and needed to adjust my W-4 for my new job. The estimator calculated everything perfectly and I ended up with a small refund of $340.

Has anyone tried both the IRS withholding estimator and TurboTax's W-4 calculator? I'm wondering which one is better for someone with large medical deductions like the original poster.

I went through this exact same situation last year with major medical expenses from a surgery, so I totally understand your confusion! The W-4 changes a few years back definitely made it more complicated. Here's what I learned after making some mistakes initially: You need to estimate ALL your itemized deductions for the year (medical expenses above 7.5% of your AGI, plus any mortgage interest, state/local taxes, charitable donations, etc.). Then subtract the standard deduction amount from that total. Only put the difference on line 4(b) of the W-4. With $27,000 in medical bills, a good chunk of that should qualify as deductible once you apply the 7.5% AGI threshold. Don't forget you can also include mileage to/from medical appointments and prescription costs. One tip that saved me: keep really detailed records of everything medical-related this year since you'll likely continue having follow-up appointments and expenses. I use a simple spreadsheet to track dates, amounts, and what each expense was for. Makes tax time so much easier! The instructions really are confusing - you're not alone in feeling lost by them. Take your time working through the calculations and don't hesitate to adjust your W-4 later in the year if your situation changes.