As usual, I filed early via Turbo Tax. I gave up doing it by hand some years ago, for reasons that include:
(1) Potential alternative minimum tax liability if you live in a high-tax jurisdiction such as New York, California, or Washington D.C. Whether one ends up owing it or not, what a hassle to have to do the computation.
(2) The nightmare of, say, forgetting $100 of gross income until you are almost done. With Turbo Tax, you just enter it and the computer does the rest. If you're preparing your return by hand, any calculation that depended on adjusted gross income has to be redone.
(3) The last time I did it by hand, there was some insane rule for capital gains, such as trivial mutual fund passthroughs, that related to tax rate changes and special rates. The IRS (through Congress's fault, not its own) had to come up with a form that required something like 15 calculations that I recall as being on the order of, "Take 19% of the amount on line 5, and subtract it from 23% of the amount on line 7. Then take the square root of the absolute value of the difference, round it to the nearest integer, and enter it on Line 12."
OK, I am admittedly exaggerating a bit on that one. But only to convey a Deeper Truth. I do indeed recall finding that, even though each calculation was mechanical, it was very hard to avoid an error (and thus to replicate the result) if one was doing very many of them in a row.
Turbo Tax, here I come, I decided - even though I have subsequently learned that this company may not be the world's best-faith political actor.
But not everyone files early, whether with Turbo Tax or not. Yesterday (April 14), as I took a late night flight from California back to NYC, the man seated next to me appeared to be doing a federal income tax return on his laptop. Good thing it wasn't April 15, as our plane was delayed and landed after midnight.