Realized I accidentally claimed exemption from federal withholding for 6 months - can I make a Q4 estimated tax payment to reduce penalties?

Yes, you can definitely still make an estimated tax payment for the fourth quarter! The deadline for Q4 estimated payments is January 15th, so you have time to figure out how much you need to pay. The IRS typically imposes a penalty if you've paid less than 90% of your current year tax or 100% of your previous year's tax (110% if your income is over $150,000). But there are a few ways to reduce or eliminate the penalty: If you can pay enough in your Q4 estimated payment to reach that 90% threshold for the entire year, you might avoid penalties completely. You'll need to calculate your total expected tax liability for the year and figure out what you've already had withheld from your first job. Another option is to increase your withholding on any remaining paychecks this year. Withholding is considered to have been paid evenly throughout the year, even if it's actually withheld later in the year, which can help reduce the penalty. Don't beat yourself up too much about this mistake - it happens more often than you'd think!

I went through something similar last year and found taxr.ai really helpful for calculating exactly how much I needed to pay to minimize penalties. After realizing I had messed up my withholding, I was completely confused about how to calculate what I owed and was worried about getting hit with massive penalties. I uploaded my paystubs and W-2 from my previous job to https://taxr.ai and it helped me figure out exactly how much I needed to withhold from my final paychecks to minimize any penalties. It also explained which penalties might apply in my situation and how they're calculated. Way clearer than the confusing IRS publications I was trying to decipher!

I was really skeptical about using taxr.ai when I mentioned it in my earlier comment, but I decided to give it a shot because I was in a similar situation with messed up withholding. I'm actually surprised how helpful it turned out to be! It analyzed my paystubs and previous year's return, then calculated exactly how much I needed to make in Q4 payments to minimize penalties. The penalty calculations were super clear - showed me what I'd owe with and without making additional payments. What really impressed me was how it explained the "safe harbor" rules in plain English and showed me exactly how much I needed to pay to meet them. Saved me hours of research and probably a few hundred dollars in penalties. Definitely worth checking out if you're trying to fix withholding issues before year-end.

I had almost the exact same situation last year! After trying for WEEKS to get through to the IRS to ask about penalty abatement options (constantly on hold, disconnected calls, etc.), I finally tried Claimyr and it was a game-changer. Instead of waiting on hold for hours, https://claimyr.com had an actual IRS agent call ME back within about 45 minutes. You can see how it works in this video: https://youtu.be/_kiP6q8DX5c The IRS agent confirmed I could request first-time penalty abatement if this was my first time making this kind of mistake, which it was. She also walked me through exactly how to calculate my Q4 estimated payment to minimize further penalties. Totally worth it to get an actual person who could address my specific situation.

I was completely wrong in my skeptical comment earlier. After struggling for THREE HOURS trying to get through to the IRS myself yesterday, I broke down and tried Claimyr. Within 35 minutes, my phone rang and it was an actual IRS agent ready to help me. The agent confirmed I could make a Q4 estimated payment to reduce penalties and gave me specific advice for my situation. She also explained I might qualify for first-time penalty abatement since I hadn't had any issues the previous three years. The best part was being able to ask follow-up questions and get immediate answers instead of trying to interpret the vague information on the IRS website. I was able to make my estimated payment right after the call and now feel much less stressed about the whole situation.

Don't forget to immediately submit a new W-4 to your payroll department too! You should probably put an additional amount to withhold from each paycheck for the rest of the year, not just the minimum required. The form has a specific line for additional withholding (Line 4c). Also, if you're going to owe a lot, maybe start setting aside money now so you're not shocked by a huge bill in April. I made this mistake before and ended up on a payment plan because I couldn't pay the lump sum.

Quick question - if OP changes their W-4 now to withhold a bunch of extra money from their last few 2025 paychecks, will that actually help with the underpayment penalty? I thought the penalty was calculated by quarter, so fixing it in December wouldn't help with the earlier quarters when nothing was withheld?

I actually just went through this exact same situation earlier this year! Made the same mistake with the exemption box and didn't notice for months. Here's what I learned: First, don't panic - this is more fixable than you think. The key thing to understand is that withholding from your paycheck gets treated as if it was paid evenly throughout the year, even if you do it all in December. This is huge because it can help with penalties retroactively. I'd strongly recommend doing BOTH things mentioned above - submit a new W-4 with maximum additional withholding for your remaining paychecks AND make a Q4 estimated payment if needed. Calculate roughly what you'll owe for the full year, subtract what was already withheld from your first job, then split the remainder between increased withholding and estimated payment. Also look into first-time penalty abatement if you haven't had issues before - it can waive penalties entirely if you qualify. The IRS is actually pretty reasonable about honest mistakes like this, especially if you're proactive about fixing it before filing. One last tip: when you do your W-4 next year, maybe set it to withhold slightly more than needed so you have a buffer. Better to get a small refund than deal with this stress again!