ISTM that’s the best argument for “they don’t bother checking postmarks” of all.
Not true. We did the math, I could take what I owe, put it in a 6 month CD in March and make more than the fees by the time I need the money in October. I’ve actually done that a couple of times. Lately, it’s just not extra stress at a time where my actual business is enough stress - which is worth paying for as long as the fee is minimal.
I got it done on time, and owed much less than I expected. Win/Win!
Good point I hadn’t considered.
If their late interest rates are below market, which they often are, you can make a small arb on late paying.
As you say, the big help is avoiding an admin flail in 1Q if your biz is naturally berserk then.
I’ve often wondered whether tax accountants file their own taxes way late for just that reason. 
e-Filed the taxes but snail mailed the check.
It was filed by my accountant and I received notification it was accepted the same day it was filed. I just called their automated hotline and they said it should be deposited in my checking account by Wednesday, April 15th. I can hold on for two more days.
For everyone who is mailing their return, I’m curious why. Are you typing up the forms manually? Using software that doesn’t support eFile, or trying to avoid the eFile charge? Something else?
Is this for financial reasons? How much interest do you earn in those couple extra days versus the cost of the envelope, stamp, and check?
Before I was married and liked to live dangerously, I frequently put my tax returns in the mail on the 16th or 17th of April.
This was in the 1990s, and I never ever had any issue with my returns being processed normally. I don’t think anyone checks postmarks on returns received in April.
In my almost 30 years of marriage I have filed our joint returns well in advance, always before April 1. I married a Tax Accountant. She has never touched our tax returns except to sign in the early days when we submitted paper returns. To be fair she hasn’t been a PRACTICING Tax Accountant for over 25 years.
Just to tweak the machine.
I wouldn’t sneer too hard. Getting a refund means you overpaid during the year, which also means you gave the US government an interest free loan. Not the smartest use of your money.
I’m a dinosaur who still uses paper checks for a number of purposes, but not for paying taxes. It’s way easier to login to irs.gov and my state website and pay electronically, and I don’t have to drive to the post office or worry about the postmark date.