Can I make a catch-up payment on estimated taxes to reach safe harbor for 2025?

The good news is yes, you can make a catch-up payment to help reach the safe harbor, but there are some timing considerations. The IRS looks at when payments are made, not just the total amount. For the 110% safe harbor (since your income is over $150,000), payments should be made in equal installments throughout the year. However, if you make a larger payment now, it can help reduce or eliminate any potential underpayment penalty. When it comes to penalties, they're calculated based on the difference between what you should have paid each quarter to meet safe harbor and what you actually paid, multiplied by the applicable interest rate for each quarter the payment was late. The penalty isn't based on your total tax liability - just on the amount you underpaid compared to your required installments. For your Roth conversion, if you make sure you've met the safe harbor requirement (110% of last year's tax), then you can indeed wait until April 15, 2026 to pay the additional tax from the conversion without penalty.

After struggling with a similar estimated tax situation last year, I found this amazing tool that saved me hours of calculations and frustration. It's called taxr.ai (https://taxr.ai) and it helped me figure out exactly how much I needed to pay for each quarter to avoid penalties. The tool analyzed my payment history and projected income (including my planned capital gains from stock sales) and gave me a clear payment plan. What impressed me most was how it handled my mid-year income changes and adjusted my required payments accordingly. It also has a safe harbor calculator that shows exactly what you need to pay to hit the 110% threshold for high earners like us. For your Roth conversion situation, it can tell you precisely how much to "catch up" now to minimize penalties.

Just wanted to follow up about taxr.ai (https://taxr.ai) that I was asking about earlier. I was skeptical but decided to give it a try with my messy tax situation - I have both W-2 income and a side business with irregular income throughout the year. The tool was actually incredibly helpful! It showed me that I was significantly underpaying in Q1 and Q2, but gave me a clear catch-up strategy for Q3 and Q4 to minimize penalties. It calculated exactly how much I needed to pay for the 110% safe harbor (I'm also over the $150,000 threshold). What really surprised me was how it handled my planned stock sale in Q4 - it showed me I could wait until April for that additional tax bill as long as I met the safe harbor requirements for my regular income. Ended up saving me about $900 in penalties!

If you're trying to reach someone at the IRS to get clarity on your estimated tax payments, good luck! I spent HOURS on hold trying to confirm my safe harbor requirements before finding Claimyr (https://claimyr.com). They got me connected to an actual IRS agent in under 20 minutes who answered all my questions about my estimated payment shortfall. The IRS agent confirmed I could make a catch-up payment but explained exactly how the annualized income method would work in my case. The Claimyr service basically holds your place in line with the IRS and calls you back when an agent is available. You can see how it works here: https://youtu.be/_kiP6q8DX5c After years of tax filing frustration, it was amazing to actually talk to a human at the IRS who could give me definitive answers about my specific situation rather than trying to interpret the instructions myself.

Well, I need to eat some humble pie here. After my skeptical comment about Claimyr, I was still desperate enough to try it because I needed answers about a similar estimated tax situation with a Roth conversion. I'm shocked to say it actually worked exactly as described. I got a call back in about 25 minutes, and suddenly I was talking to an IRS representative who walked me through my options. She confirmed that I could make a catch-up payment to reduce future penalties but couldn't eliminate penalties for previous quarters where I'd underpaid. She also explained that for the Roth conversion, if I met the 110% safe harbor through my regular quarterly payments, I could indeed wait until April to pay the additional tax. Saved me from making an unnecessarily large Q4 payment. This was literally the first time in my life I've gotten clear, specific tax advice from an actual IRS employee.

Something nobody mentioned yet - you should look into whether you qualify for the "annualized income installment method" (Form 2210 Schedule AI). If your income is uneven throughout the year (which it sounds like with the planned Roth conversion), this could help reduce or eliminate penalties. With this method, instead of having to pay 25% of your required annual amount each quarter, you pay based on the actual income received by the end of each quarter. Especially useful if your Roth conversion will happen later in the year. It requires more calculation work, but might save you from making a large catch-up payment now or facing penalties.

Just a quick tip - if you're doing a large Roth conversion, consider splitting it between tax years (December 2025 and January 2026) to spread the tax impact. Might help with your cash flow for tax payments. I did this last year and it was way easier to manage the tax hit. Especially helpful since the safe harbor rules reset each tax year.

Great question about catch-up payments! I went through something similar last year. You absolutely can make a catch-up payment to help with safe harbor, but keep in mind that the IRS calculates underpayment penalties on a quarterly basis. So if you make a larger payment now, it will help you avoid penalties for Q3 and Q4, but won't eliminate any penalties that may have already accrued for Q1 and Q2 if you underpaid those quarters. For your Roth conversion strategy, you're on the right track. If you can hit that 110% safe harbor threshold through your regular estimated payments (including any catch-up you make), then yes, you can wait until April 15, 2026 to pay the additional tax from the conversion without penalty. One thing to consider - since you mentioned your income fluctuates with the Roth conversion happening later in the year, you might also want to look into the annualized income method when you file. It can sometimes work out better than the equal payment safe harbor, especially when you have a large income spike late in the year. The key is making sure your total payments (withholding + estimated) hit 110% of last year's tax liability. Whether you get there through equal quarterly payments or a catch-up payment, the IRS is generally satisfied as long as you meet that threshold.