TriNet, a San Leandro, Calif.-based professional employer organization acquired ExpenseCloud, a software-as-a-service provider that allows companies to manage expense reporting online or from a mobile device. ExpenseCloud’s offering lets firms create, submit and approve expense reports online and then integrate with accounting software to reimburse employees or invoice clients. ExpenseCloud is three years old and based in Los Angeles.

ExpenseCloud will operate as a business unit of TriNet, with its brand remaining intact. ExpenseCloud co-founder and CEO Eric Sikola and co-founder and Chief Technical Officer Dan Fritcher will remain in leadership positions in the new business unit.

TriNet plans to retain all ExpenseCloud employees and will incorporate the company’s offering into its client service platform later in 2012.