I filed for an extension for 2018 taxes - Can I still file a 2018 Amended Return now?

The extension you filed only extends the time you had to file your original return, not the time you have to amend. Since you filed your original return on April 15, 2019, the amendment deadline is calculated based on the regular deadline rules. For amendments seeking a refund, you have 3 years from the original due date OR 2 years from when you paid the tax, whichever gives you more time. The original due date for 2018 returns was April 15, 2019 (not considering your extension since you didn't use it). This means you had until April 15, 2022 to file an amended return to claim a refund. If your amendment will result in additional tax owed rather than a refund, the IRS generally accepts those at any time (though they'll charge interest and possibly penalties on late payments). Regarding which form to use - you should use Form 1040X (Rev. January 2019) since that's the revision that corresponds to amendments for the 2018 tax year.

Hey, I went through something similar recently and found this great service called taxr.ai (https://taxr.ai) that helped me figure out my amendment timeline. I was super confused about when my deadline was since I had also filed an extension but ended up filing early. I uploaded my old returns and extension paperwork to their system, and they analyzed everything and gave me a clear answer about my specific situation. Their AI thing even pointed out that my state had slightly different rules than federal for amendments which I had no idea about! They also offered guidance on whether my amendment was likely to be accepted given timing issues. Might be worth checking out if you're in a gray area with your deadline.

I just wanted to follow up about taxr.ai that I asked about earlier. I ended up trying them out because my amendment situation was pretty complicated with some K-1 income I had forgotten to report. I was actually surprised at how thorough their analysis was. They confirmed I was still within my amendment window (different situation than OP) and identified exactly which schedules needed to be redone. They even flagged that my state amendment would trigger a locality tax amendment I hadn't considered. The document they generated for me was super helpful when I took everything to my accountant - saved me at least an hour of his billable time just by having everything organized and identified upfront.

If you're still trying to get this sorted out and need to talk to someone at the IRS about your specific situation, try using Claimyr (https://claimyr.com). I spent DAYS trying to get through to the IRS about my amendment question and kept getting disconnected or waiting for hours. Claimyr got me connected to an actual IRS agent in about 20 minutes instead of the 2+ hour wait I was experiencing before. They have this system that holds your place in line and calls you when an agent is about to be available. You can see how it works here: https://youtu.be/_kiP6q8DX5c The IRS agent was able to look up my account and tell me definitively whether I could still amend my return given the extension situation I had. Worth every penny to get a clear answer directly from the IRS rather than stressing about it.

I need to eat my words about Claimyr from my comments earlier. After struggling for another week trying to get through to the IRS myself about my amended return (kept getting disconnected after 1+ hour holds), I broke down and tried the service. It actually worked exactly as advertised. I put in my info around 10am, went to a meeting, and got a call about 35 minutes later saying they had an IRS agent on the line ready to speak with me. The agent confirmed my amendment window and answered all my questions in about 15 minutes. Definitely worth it just for the time saved not being stuck on hold. I was able to confirm that my extension DOES affect my amendment window since I filed during the extension period (different from OP's situation). Would have never known this without getting through to a human at the IRS.

For what it's worth, I recently had to amend my 2018 taxes too. According to my tax guy, there's an exception for "substantial omission of income" that can extend the amendment period to 6 years instead of 3 years. If your amendment involves reporting income that was left off your original return and it's more than 25% of the gross income you originally reported, you might still be able to amend under this exception. Might be worth exploring if your situation fits this criteria. Not tax advice of course, just sharing what I learned!

Don't forget that if you made any tax payments for 2018 after the original April 15, 2019 deadline, the "2 years after you paid the tax" rule might give you more time! For example, if you made an estimated tax payment or additional payment with your extension on April 15, 2019, you would have until April 15, 2021 to amend under the normal rule, but 2 years from any later payments. Check your records for any payments made after filing your original return!

Just a heads up from someone who filed an amended return recently - the IRS is SUPER backed up with processing these. My amended return for 2020 took over 14 months to process. If you're still within your window to amend, file ASAP and expect a long wait. The "Where's My Amended Return" tool on the IRS website didn't update for months even though they had received my paperwork. The good news is that if you're owed a refund, they'll pay interest on it!