The U.S. Postal Service will have three Puget Sound area post offices open until midnight Monday for people who wait until the last minute to file their tax returns. Midnight is when they must be postmarked.

  • Riverton Station, 15250 32nd Ave. S., Seattle. (The retail office at Riverton Station will close at 6 p.m.)
  • Tacoma Mail Processing Center, 4001 S. Pine St. (The collection box is on S. 42nd St. on the south side of the building.)
  • Everett Mail Processing Facility, 8120 Hardeson Rd.

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Related:Need more time to file your taxes?

USPS reminds you to make sure your tax return has sufficient postage. First-Class postage is 46 cents for the first ounce and 20 cents for each additional ounce. If you are mailing a number of supplementary forms and schedules with your return, the envelope is likely to weigh more than one ounce.

The IRS will not pay postage due. Mail with insufficient postage is returned to sender. If you are in doubt about how much postage to apply, use a lobby scale or ask a postal clerk for assistance.

If possible, mail your return using the pre-addressed envelope provided by the IRS. If you must prepare another envelope, make sure the address is legible and include your return address.

When mailing your return at a post office not on the list for late pickup, check the times posted on the blue collection box to determine the last scheduled pickup time.

If you have a refund due to you from 2009, but haven't filed a return for that year, you need to get it filed by midnight. Otherwise, the government keeps that money.

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