The United States Postal Service has plans to accommodate the parade of people pursuing a postmark proving punctual posting of their tax returns.

All area Post Office retail windows will be open with regular customer service hours on Tuesday, April 15. No Northern Colorado offices will be staying open late. The Denver GMF retail office at 7500 E. 53rd Place will be open until midnight. 

Accepting Returns Until Midnight 

The following offices will accept tax returns for postmarking only up to 12 midnight. No stamps will be sold at these locations after hours.

  • Longmont Main Post Office, 201 Coffman St.
  • Loveland Main Post Office 446 E. 29th St.

Please note - the Fort Collins Post Office IS NOT accepting returns for postmarking up to midnight. 

Tax Mailing Tips

  • Apply the proper postage or stamps, especially if enclosing extra forms and schedules.
  • Using a regular size Number 2 envelope, First Class postage costs 49 cents for the first ounce.
  • For heavier envelopes, add extra stamps or postage amounting to 20 cents for each additional ounce.
  • If you are not sure about the correct postage, it is best to add additional stamps, or take your forms to the Post Office to ensure that correct postage is applied.
  • Make sure you print the proper IRS address on the front of the envelope.  
  • Print your return address in the upper-left-hand corner of your tax mail envelope.
  • Customers who wish certification that their tax mail form was sent, should send it Certified Mail
  • Customers with IRS tax questions can contact the IRS at 1-800-829-1040; or go to