It's tax day, April 15.

If you're planning to mail your taxes at the last minute, several post offices around the state will be open to help.

The IRS expects approximately 138 million Americans, including nearly 2.2 million Coloradoans, to file tax returns this year with an estimated 43 percent of them using the mail.

The IRS says 20 percent of Americans wait until the last week to file or mail their return.

Here's the list of the Colorado post offices open until midnight:

Denver General Mail Facility, 7500 E. 53rd Pl. (N. Quebec & I-70)

Denver Downtown Station, 951 20th St.

Boulder Valmont Station, 2995 55th St.

Colorado Springs General Mail Facility, 3655 E. Fountain Blvd.

Grand Junction Foresight Mailhandling Annex, 602 Burkey St.

Littleton Highlands Ranch Post Office, 9609 S. Univ. Blvd.

Longmont Main Post Office, 201 Coffman St.

Longmont Twin Peaks Mail Processing Center, 1845 Skyway Dr.

Loveland Main Office, 446 E. 29th St.

Pueblo Main PO, 1022 Fortino Blvd.

Here's the list of the Colorado post offices open until 10 p.m.:

Bear Valley Station, 7555 W. Amherst Ave.

Capitol Hill Station, 1571 Marion St.

Cherry Creek Station, 245 Columbine St.

Lakewood Station, 10799 W. Alameda Ave.

Mile High Station, 1421 Elati St.

Montclair Station, 8725 E. 11th Ave.

Northglenn Station, 11887 Washington St.

North Pecos Station, 1411 Cortez St.

South Denver Station, 225 S. Broadway

Sullivan Station, 8700 E. Jefferson Way

University Park Station, 3800 Buchtel Blvd.

The Salida Post Office at 310 D St. will be open until 11 p.m.

Customers can also call the postal customer line at 1-800-ASK-USPS (1-800-275-8777) to find late tax mail collection sites.