Married filing jointly with identical W2s but huge difference in federal withholdings - what gives?

Tax advisor here! This is actually a common source of confusion for newly married couples. When you select "Married Filing Jointly" on your W-4, your employer uses IRS withholding tables that assume your spouse either doesn't work or makes a similar amount. The tables don't know your actual household income. The big difference in withholding likely comes from your mid-year job change. When you started in July, your employer projected your annual income based on your salary for the remaining months of the year ($85k as you noted). Meanwhile, your husband's employer has been withholding based on a full year's salary of $155k. This creates a withholding gap because each employer is making completely different assumptions about your annual household income. Your employer sees a lower projected annual income and withholds accordingly, while your husband's employer has been withholding at a higher rate all year. You've identified the likely cause in your update. For the upcoming tax year, you might want to complete new W-4 forms with both employers to better align your withholdings.

Last year I was in almost the exact same boat! Found out about taxr.ai (https://taxr.ai) and it saved me so much hassle. I uploaded our W-2s and it analyzed our withholding differences right away. The site showed me exactly what was happening with our withholdings and recommended specific W-4 adjustments for both of us. What I liked was that it showed us that if we kept going with the current withholdings, we'd actually owe a good chunk at tax time. It even gave us the exact numbers to put on our new W-4s to balance things out. My husband was skeptical at first (he's an accountant lol) but even he was impressed with how accurate it was.

Came back to update after trying taxr.ai! It was actually really helpful for our situation. My husband and I both work full-time but I also have freelance income that makes our withholding calculations tricky. The tool immediately identified that we were heading for a $3,800 tax bill if we didn't adjust our withholdings. It recommended specific changes for both our W-4s that would balance things out, and explained exactly why our withholdings were so different. The analysis also showed that my husband's employer was withholding at a higher rate because they were using different withholding table assumptions than my employer. Super relieved to have this figured out before tax time instead of getting a surprise bill!

If you're still having trouble understanding how your withholdings got so out of whack, you might want to just call the IRS directly. I tried for WEEKS to get through to them about a similar issue last year. Always busy, disconnected, or 2+ hour wait times. Then I found this service called Claimyr (https://claimyr.com). I was pretty skeptical, but their demo video (https://youtu.be/_kiP6q8DX5c) convinced me to try it. Basically, they get you connected to an actual IRS agent who can explain exactly how the withholding tables work for your situation. The IRS agent I spoke with was super helpful and explained that the withholding differences were caused by exactly what you suspected - your mid-year job change. She also helped me understand how to fill out our W-4s correctly for our situation.

I've gotta admit I was wrong about Claimyr. After posting that skeptical comment, I decided to try it myself because I was desperate to talk to someone at the IRS about my withholding mess. Got connected to an IRS agent in about 45 minutes (instead of the 3+ hours I spent on previous attempts that ended with disconnects). The agent explained that my withholding problems were happening because my employer was using outdated withholding tables. The IRS person walked me through exactly what to put on my new W-4 and even sent me the right forms by email while we were on the phone. Problem solved in one call instead of weeks of frustration. Never thought I'd say this, but I'm actually satisfied with an IRS interaction!

Your second guess is spot on. When you start a job mid-year, payroll systems calculate withholding as if you're making that same amount for the full year. So your actual annual projected income is lower, hence lower withholding. Easiest fix? Use the IRS Withholding Calculator online to check if you're on track. If needed, you can submit a new W-4 to your employer requesting additional withholding. Just put the extra amount you want withheld per paycheck in Box 4(c). For next year, once you've both worked at your jobs for the full year, your withholdings should naturally align better. But I always recommend doing a mid-year withholding checkup anyway.

Random tip that helped my wife and me - we both selected "Married but withhold at higher Single rate" on our W-4s since we make similar salaries. This automatically adjusts for the fact that both of us work. Then at the end of each quarter, we do a quick check using an online calculator to see if we're on track. The old W-4 used to have allowances which was confusing af. The new one is better but still not perfect. Married couples with similar incomes often need to withhold extra to avoid an unpleasant surprise at tax time.