Onyx Software Corp completed its initial public offering on Friday, selling 3.1 million shares at $13 each. The issue was well received, trading as high as $26, before closing at $23.5625, up more than 81% from the offering price. Volume for the session, in which Onyx was the most advanced stock on Nasdaq, was 6.3 million shares. Bellevue, Washington-based Onyx provides enterprise relationship management software, which automates the functions that enable companies to manage and maintain customers and partners. The company’s products are based on Windows NT and BackOffice platforms and feature a common data model that creates a single repository of marketing, sales and service information that is accessible to multiple audiences via the internet. The company currently boasts about 350 customers. The shares are trading on the Nasdaq National Market under the symbol ONXS. Credit Suisse First Boston Corp, SG Cowen Securities Corp and Piper Jaffray Inc served as managing underwriters for the offering.