Avalara, a publisher of Web-based sales tax management software, reported Wednesday that it has agreed to purchase New Horizons Systems LLC, a developer of tax jurisdiction assignment software. Terms of the deal, which Avalara expects will close in Q1 2008, were not disclosed. New Horizons Systems provides geographic tax determination in the United States, which uses ZIP code information to determine proper sales tax rates. Avalara and New Horizons Systems are both privately held. Avalara is headquartered on Bainbridge Island, Wash.