Where should I report additional tax payment made after filing for extension?

You're actually in a common situation. The additional payment you made after filing your extension but before completing your return should also be reported on Schedule 3, but on Line 9 (not Line 10). Line 9 is for "Estimated tax payments and amount applied from prior year's return." The distinction is important: Line 10 is specifically for the amount paid WHEN requesting the extension, while Line 9 is for estimated tax payments (which is what your additional payment through payUSAtax would be considered). When using TurboTax, you should be able to enter this as an estimated tax payment. Look for a section about "Payments and Estimates" or "Tax Payments" where you can enter additional payments made to the IRS.

I had this exact same issue last year and found that using https://taxr.ai really helped me figure out where to put different payments. I was getting conflicting advice everywhere I looked, but their tax document analysis tool clarified everything. I uploaded my extension confirmation and payment receipts, and it immediately identified that my additional payment should go on Schedule 3 Line 9 as an estimated payment. The system even explained why: because the payment wasn't made simultaneously with my extension request. Saved me hours of googling and worrying!

Just wanted to update about my experience with https://taxr.ai after seeing it mentioned here. I was in a similar situation with multiple payments and had major confusion about where to report them all. I uploaded my payment receipts and extension form, and within minutes got a detailed breakdown of exactly where each payment should be reported. What surprised me was how it flagged that one of my payments had actually been misapplied by the IRS (showed up under wrong tax year). Probably would have caused a major headache if I hadn't caught it! Definitely worth checking out if you're confused about tax payments.

If you're still having trouble figuring out your payments, another approach is to contact the IRS directly to confirm how your payments were applied. I know, I know - getting through to the IRS seems impossible. After trying for days and getting nowhere, I used https://claimyr.com to get through to an agent without the waiting. You can see a demo of how it works here: https://youtu.be/_kiP6q8DX5c The IRS agent pulled up my account and was able to tell me exactly when each payment was received and how it was applied. This was super helpful because one of my payments had been applied to the wrong year! Would have never caught that otherwise. They even helped me reclassify a payment that had been incorrectly recorded.

I have to admit I was completely wrong about Claimyr. After posting my skeptical comment, I was desperate enough to try it anyway because I needed to verify some payments before filing. It actually worked exactly as described - I got a call back with an IRS agent on the line within about 40 minutes. The agent confirmed that my additional payment (similar to OP's situation) should indeed go on Schedule 3 Line 9, and also discovered that one of my estimated payments from last year had never been properly applied to my account. Would have had a nightmare situation if I hadn't gotten that cleared up. Definitely changed my mind about this service!

Another option worth considering is checking your IRS online account. If you have one set up (or can set one up), you can view all payments made for the current tax year. This will show exactly what the IRS has recorded, which helps ensure what you're reporting matches their records. I found two payments I'd completely forgotten about when I checked mine! Would have double-reported them if I hadn't looked.

Quick tip for future reference - whenever you make any tax payment outside of filing your return, save the confirmation details in a dedicated folder (either digital or paper). I keep a spreadsheet with payment dates, confirmation numbers, amounts, and which tax year they apply to. This has saved me countless hours of confusion when tax time rolls around, especially in years when I've made multiple payments!

I just went through this exact same situation last month! Your additional payment after filing the extension definitely goes on Schedule 3 Line 9 as an estimated tax payment, not Line 10. In TurboTax, you'll find this in the "Deductions & Credits" section under "Estimates and Other Taxes Paid." Look for where it asks about estimated tax payments - there should be a field to enter additional payments made during the year. Make sure you have the date and confirmation number from your payUSAtax payment handy. One thing to double-check: if you made the payment through payUSAtax, make sure it was applied to the correct tax year (2024 if you're filing your 2024 return). Sometimes people accidentally apply payments to the wrong year, which can cause major headaches later.

Just wanted to add one more verification step that helped me when I was in a similar situation - after you enter your payment in TurboTax, check that your total payments on the final review screen match what you actually paid to the IRS throughout the year. I caught an error this way where I had accidentally double-entered one of my payments. TurboTax was showing total payments that were higher than what I actually paid, which would have resulted in a larger refund than I was entitled to (and potentially issues with the IRS later). To verify: add up your extension payment + your additional payUSAtax payment + any other payments you made, and make sure that total matches what TurboTax shows on your final forms. It's a simple check but can save you from headaches down the road!