Heidi Valentine, a CPA with Connie’s Tax Service, kept the calculator tape from the more than 500 clients she has done taxes for this year. This year, because the April 15 falls on a Sunday, taxpayers have until Tuesday, April 17, to get their taxes in the mail. The Kalispell Post Office on North Meridian will be open regular hours Tuesday, but mail dropped off after hours into the front lobby slot or boxes on the side of building will be collected at midnight, and post office employees will make sure the letters get an April 17 stamp.