Why is my 2025 federal withholding so low on my main job? Did I mess up my W-4?

The issue is likely related to the W-4 changes that happened in 2020. The IRS completely redesigned the W-4 form and eliminated allowances entirely. The old system of claiming allowances doesn't exist anymore. When you selected Head of Household on your W-4 but didn't provide any additional information (like dependents or other income), the payroll system likely calculated your withholding based solely on your income from that job, assuming it was your only income. Since Head of Household has more favorable tax brackets than Single, less tax was withheld. The problem gets compounded when you have multiple jobs. Each employer withholds as if their job is your only income, not knowing about your other jobs. This often results in underwithholding when you combine all income sources on your tax return.

I went through something similar last year and discovered taxr.ai (https://taxr.ai) which really helped me understand what was happening with my withholdings. I uploaded my W-2s and paystubs, and it broke down exactly why I was under-withheld and simulated different W-4 configurations to fix the issue. What I learned was that the new W-4 system is actually designed to be more accurate, but only if you fill it out completely. Most people (like me) just check a filing status and call it done, which causes problems especially with multiple jobs.

Just wanted to update after trying taxr.ai - it was actually super helpful! I uploaded my last few paystubs and it immediately showed why I was being under-withheld. Turns out I had checked a box on my W-4 that I shouldn't have, plus having multiple jobs was throwing everything off. It generated a completed W-4 for each of my employers with the exact amounts I should put on each line. I turned those in last week, and my latest paycheck already shows a more appropriate withholding amount. Wish I had known about this earlier in the year instead of waiting until I was doing my taxes.

If you're already stuck owing taxes and need to speak with the IRS to set up a payment plan, I highly recommend Claimyr (https://claimyr.com). I spent DAYS trying to get through to the IRS about my withholding issue last year and kept getting disconnected or waiting for hours. I was super frustrated and found Claimyr through a YouTube video (https://youtu.be/_kiP6q8DX5c). The service basically holds your place in the IRS phone queue and calls you when an agent is about to answer. Saved me literally hours of hold time, and I got my payment plan set up in one call.

I have to admit I was wrong about Claimyr. After my frustrated comment, I decided to try it anyway since I was desperate to resolve my tax issue. I expected it to be a waste of money, but I actually got through to an IRS agent in my first attempt. The service sent me a text when an agent was about to pick up, I got on the call, and finally resolved the payment plan I'd been trying to set up for weeks. The agent even helped me understand some withholding issues similar to what the original poster described. I'm still not happy about owing taxes, but at least I'm not spending my life on hold anymore.

Just a tip - if you're getting a big refund one year ($8-10k) and owing the next, your withholding needs a major adjustment regardless of which forms you're using. Ideally, you want to be close to zero (maybe a small refund). The new W-4 actually has a specific multiple jobs section. If you have 5 W-2s, you DEFINITELY need to account for this or you'll be severely under-withheld. The simplest approach for multiple jobs is to check the box in Step 2(c) on your highest-paying job's W-4, and check "Single" even if you're Head of Household. This withholds at a higher rate to account for the stacking of incomes.

Head of household vs single makes a HUGE difference in withholding. I made this exact mistake and owed $2200 last year. The new W4 is so confusing compared to the old one with allowances.

I went through something very similar when I moved states and started a new job. The combination of multiple W-2s and selecting Head of Household without properly accounting for your other income sources is definitely what caused your underwithholding issue. One thing that helped me was setting up quarterly estimated tax payments for situations like this. Since you know you'll likely owe again if you don't adjust your withholding, you could make estimated payments throughout 2025 to avoid penalties and the stress of owing a large amount at tax time. For your W-4 fix, I'd recommend using the IRS Withholding Estimator online rather than guessing. It will ask about all your jobs and give you specific amounts to withhold from each employer. Much more accurate than trying to figure out the multiple jobs worksheet manually. Also, keep in mind that owing $1,300 on multiple W-2s isn't necessarily a disaster - it just means your withholding was off. The goal is to get as close to zero as possible for next year so you're not giving the IRS an interest-free loan or scrambling to pay a big bill.

The good news is that owing $1,300 isn't catastrophic - it just means your withholding system needs an overhaul. I've been through similar situations with multiple W-2s, and it's almost always fixable with the right W-4 adjustments. Here's what I'd recommend for your immediate situation: First, if you haven't filed yet and need to pay what you owe, you can set up a payment plan directly with the IRS online. No need to call if you owe less than $50,000 - their online payment agreement tool is actually pretty straightforward. For fixing 2025, the Multiple Jobs Worksheet on the W-4 is your friend, but I get that it looks intimidating. The IRS Withholding Estimator online does the same calculations but walks you through it step by step. You'll need your most recent paystubs from all jobs, and it will tell you exactly what to put on each employer's W-4. One key thing - Arizona doesn't have special state withholding rules that would affect your federal taxes, so your move there isn't the culprit. It's really just the combination of Head of Household status (which assumes you're supporting dependents and withholds less) plus multiple income sources that each employer calculates in isolation. The quickest fix while you figure out the precise numbers is to change your highest-paying job's W-4 to "Single" status and add maybe $75-100 extra withholding per paycheck on line 4(c). You can always adjust it later once you run the numbers properly.