"I've been told that sometimes the 15th is dead and sometimes it's a zoo," he said. "You know, people who procrastinate don't get up this early."

This is the busiest H&R Block office in the country, processing about 8,000 returns a year, he said. His tax preparation specialists ­ there are 46 of them over two shifts ­ will be working until midnight, mostly processing electronic returns.

During the rest of the year, the office closes at 9 p.m.

"This being the last day, I imagine we will be taking customers until they stop walking through the door," he said.

Some will come through the door with a shoebox full of information, he said, and some will arrive carrying tax forms at arm's length "like it's something nasty."

Most Americans don't wait until the last moment. The Internal Revenue Service says only about 25 percent of the taxpaying population files in the last week, said Shawn George, an IRS spokeswoman.

So far, the average federal return is $1,988.

In Hawai'i, about 401,000 people had filed their returns by the end of last week, she said. Nearly 175,000 of them filed electronically.

Returns can range from 10 days for those who file electronically and have direct deposit to six to eight weeks for people who want the government to put the check in the mail, she said.

The IRS has three walk-in offices here ­ in Honolulu, Wailuku and Hilo ­ and expects about 600 people will stop by for forms or to ask questions, she said. About 8 percent will file for an extension.

The U.S. Postal Service expects brisk business tonight as last-minute filers engage in an annual tradition: the post office drive-by drop-off. Hawai'i Postal Service workers will have curbside service until 10 p.m. at the downtown office on Richards Street and at the main office next to Honolulu International Airport.