Private equity firm K1 Investment Management has acquired a majority stake in expense management firm Certify for $125 million and will merge it with its three other spend management firms: ExpenseWatch, Nexonia and Tallie. Certify claims that the new, privately held entity forms the largest expense management competitor to Concur, which is owned by the publicly held SAP. That claim is based on the four brands' more than 7,500 corporate clients.