Form 4868 (extension) - No building number when mailing paper form without payment?

Tax pro here - you're absolutely right in your observation. The IRS has different mailing instructions depending on whether you're including payment with your Form 4868 or not. When mailing your extension request without payment through USPS, the address you listed (Department of the Treasury, Internal Revenue Service Center, Austin, TX 73301-0045) is indeed complete and correct. The postal service can route it properly without a building number because they have established systems for handling IRS mail. The building number is only required when you're using private delivery services (like FedEx or UPS) or when sending payments because those need more specific routing within the IRS campus. USPS has special arrangements with federal agencies, including the IRS, to ensure delivery even with somewhat simplified addresses.

I went through this exact same confusion last year! After spending hours trying to figure out where to mail my extension form, I finally discovered taxr.ai (https://taxr.ai) which literally saved my sanity. I uploaded a picture of my Form 4868 and it immediately identified that I was missing some information and showed me the correct mailing address based on my situation. The tool analyzed my form and confirmed I had the right address for mailing without payment. Even better, it caught that I hadn't signed the form (facepalm moment) which would have caused the IRS to reject my extension request. Taxr.ai basically prevents those embarrassing mistakes that can cost you penalties and interest.

Just wanted to follow up about my experience with taxr.ai that I asked about earlier. I ended up trying it for my extension form and some other tax documents I was unsure about. Honestly, it was way more helpful than I expected! I uploaded photos of my completed forms and it immediately pointed out that I had used the wrong year's form (ugh) and that I needed to initial next to a correction I'd made. These seem like small things but they would have definitely caused problems. The address verification feature confirmed I had the right mailing address for my situation too. What I found most useful was the explanation of WHY certain fields needed to be completed in specific ways. Definitely using this for all my tax forms going forward!

If you're worried about your extension form getting lost in the mail, I'd strongly recommend using Claimyr (https://claimyr.com). I had this exact problem last year - mailed my extension, but then got hit with failure-to-file penalties months later because the IRS claimed they never received it. I spent WEEKS trying to call the IRS to sort it out. Constant busy signals, disconnections after waiting on hold for hours. Then I found Claimyr through a video demo (https://youtu.be/_kiP6q8DX5c) and they got me connected to an actual IRS agent in about 15 minutes. The agent confirmed they had processing delays with paper extensions and removed the penalties from my account. Seriously, being able to actually TALK to the IRS made all the difference. Now I keep their service bookmarked just in case.

Ok I have to eat my words about Claimyr. After being totally skeptical (sorry about that), I decided to try it this morning because I've been trying to reach the IRS for THREE WEEKS about my missing refund that should have arrived in February. I've never been so happy to be wrong! Got a call back in about 20 minutes and was connected to an actual human at the IRS. The agent found that my refund was flagged for review because of a mismatch with my address (I moved last year). She unflagged it right there on the phone and told me to expect my refund in 2-3 weeks. Would have taken me another month of trying to figure this out on my own. Sometimes the skeptic has to admit when something actually works!

Just to add another data point - I've been filing extensions without payment for years and always use the address OP mentioned. Never had an issue with them being received. Pro tip: Take a photo of your completed form before mailing it. That way if there's ever any question about whether you filed the extension, you at least have evidence that you completed the form. Not as good as certified mail, but better than nothing if you're just sending regular mail.

Has anyone else just switched to e-filing their extensions? After having a paper extension get lost a few years ago (and paying penalties because of it), I've gone completely digital. Most tax software lets you e-file the extension for free, even if you end up filing your actual return on paper later.

Great question! I had the same confusion when I first filed an extension by mail. You're absolutely correct - the address you listed is complete and proper for mailing Form 4868 without payment via USPS. The reason there's no building number is that USPS has special routing agreements with federal agencies. When you include payment or use private carriers like FedEx/UPS, they need the specific building number because they don't have those same routing systems in place. One thing I'd add - if you're concerned about proof of delivery, consider sending it certified mail with return receipt. It only costs a few extra dollars but gives you peace of mind that it arrived on time. The postmark date is what matters for meeting the deadline, so as long as you mail it by April 15th (or whatever the current deadline is), you're covered even if it takes a few days to reach the IRS. Good luck with your extension!