The deadline is Monday, April 16, with the emphasis on "dead."
Monday is the last day that mail can be postmarked to the IRS containing tax returns. After that, there is a price to be paid.
"Normally, we don't have a lot of last-minute rushers. It's not like Denver or a metro area where you see lines of people at the Post Office as the deadline approaches," said a Postal employee, who wished to remain anonymous. "We won't be keeping someone here until midnight collecting last minute drops; it's just not cost-effective for a place like Craig.
"Smaller towns historically don't have a large rush of people like what happens in Denver. I would surprised if there are two dozen letters between 5 p.m. and midnight.
"On Tuesday morning, we'll sweep through the mail and if a tax envelope catches our eye, we'll pull it out and postmark it for the April 16, but if we don't catch it, it's not our problem."
If someone is caught in a bind and can't file on time, there are ways to avoid penalties.
"There are several ways a person can get an extension," said Lynn Villard, of Hamilton & Villard, LLC. "If you're running late, you can apply over the phone, by the internet, or through the mail. The forms to mail for an extension should still be available at the post office, or offices of accountants.
"The extensions only cover the actually filing. If someone owes money, that money has to mailed by Monday," she said. "If you have no idea about what you owe and don't want to pay a penalty, you can pay 110 percent of what you paid last year. Even if it's not the total that you owe, you will only be charged interest on the balance and will not have to pay a penalty."
If someone tries to guesstimate their total and they end up paying less than 90 percent of the total amount, they will face both penalties and interest, Villard said.
Only those who owe taxes must file by the April 16 deadline. Those receiving a refund have until Oct. 15 to file.