Don’t misread your calendar today. It’s April 15, and for taxpayers who have yet to file a tax return, it’s the last chance to avoid some hefty penalties.

Postal officials today will keep the doors at the post office’s downtown location, 645 Vt., open until midnight to accommodate what is expected to be a rush of last-minute filers.

Tax professionals also are giving some last-minute advice to people waking up today without a completed tax return — think extension.

Jim Long, of the Lawrence accounting firm Bogner & Long, says many times it is better for people to fill out a simple form asking for an extension rather than rushing through the sometimes complicated tax-return process.

The IRS automatically grants a four-month extension to anyone who fills out Form 4868. The one-page document takes far less time to complete than the average tax return, Long said.

But he also cautioned people that the extension isn’t a good way to postpone the pain of paying a tax bill. That’s because as part of the extension process, the IRS asks taxpayers to estimate how much taxes they still owe. Taxpayers must pay that estimated amount when they file for the extension, or else pay a penalty and interest when they file their actual return.

“It is an extension to file, not an extension to pay,” Long said. “The IRS definitely wants its money now.”

The penalties and interest, which also apply to people who ignore the deadline entirely, can be significant. Depending on how late taxpayers file their returns, the penalty can be between 5 percent and 25 percent of the total tax owed. The interest rate the IRS charges fluctuates, but it currently is around 6 percent.

Kansas taxpayers who receive the federal extension automatically receive a four-month extension for their state taxes as well.

Long said he thought there might be a few more late filers in Lawrence than in previous years.

Letter carrier Gary Washburn empties mail boxes behind the downtown Lawrence post office. Today is the deadline to mail your taxes, and the post office downtown will remain open until midnight for late filers.

“I think the economy is what’s up with that,” Long said. “I think a lot of people are in flux, going from one job to another. I think doing a tax return has become a more secondary concern for a lot of people.

“Plus, we always see a pickup in business after the Jayhawks are done playing basketball, and since they went to the Final Four, that made for a lot of people coming in later than usual.”

Lawrence Postmaster Bill Reynolds reminded area residents that only the downtown post office location would be open until midnight.

He also said that due to security issues, post office employees would not be able to hand-stamp the postmark date on envelopes dropped off by taxpayers. The stamp is what IRS officials use to determine if the return was filed on time. Many taxpayers like to see a postal employee place that stamp on their envelope, but Reynolds said regulations now require that be done by machine in Kansas City.

Reynolds says postal customers who drop off their return at the downtown post office before midnight still will receive the April 15 postmark.

Late filers will be treated to some entertainment at the downtown post office. The Alferd Packer Memorial String Band will continue its tradition of performing in the post office lobby from 9 p.m. to midnight.