Plenty of Lawrence residents missed this year’s tax-filing deadline because they thought the downtown post office was going to be open until midnight – but it closed at 7 p.m.

So what’s going to happen to those who missed the deadline?

If they’re due a refund, nothing.

If they owe money, they’ll be assessed a penalty and interest.

For the IRS, the fee is 5 percent per month based on the amount owed, and interest is charged at an annual rate of 7 percent. The state of Kansas charges people a penalty of 1 percent per month, with an 8 percent annual interest rate.

Some Lawrence residents used a postage meter in the lobby of the post office Monday night to obtain a stamp that had an April 17 date, even after the office was closed.

It was a nice try.

“Postage stickers purchased from a post office do not constitute proof of timely filing,” said Michael Devine, an IRS spokesman.

Still, Devine said if people were worried their return didn’t get in the mail on time, the best thing to do was wait for a notice of penalty to arrive in the mail. At that point, they can appeal the penalty, which can be waived if there’s good cause.

“If you think it’s late, wait until the IRS tells you it’s late,” he said.