I grew up the child of a CPA, so along with a tendency to mutter damn smum-sucking federal government at random moments I also have some more useful tax knowledge floating about my head.

So, anyhow, sumdugshi (I'm sure I got that wrong, sorry) is right on with the extension stuff and the armed goon stuff. ^_^ As to how do you know if they've got your return - I always ask the post office for a receipty thing. I wish I could remember the exact name of it - there are three different things you can pay for that'll prove you sent the thing off on time. One of them (the most expensive) also sends you back in the mail a card when the IRS gets your stuff. I usually go with the cheapest one, with gives me proof of postmark if any goons show up looking for my return.

Like I said, don't know the name, but I just ask the postal person for "that thing that proves I sent it. The cheapest one." That always works. :D It's about a dollar, I think.