RingCentral has closed its series B funding, raising $12 million from new lead investors DAG Ventures and NCD Investors and returning investors Sequoia Capital and Khosla Ventures. RingCentral also announced that it surpassed 50,000 active customer accounts, doubling its customer base in one year. Accounts range from one to many subscribers, typically in small businesses with 20 or fewer employees.

The company will use the new funding to enhance its products and services, build new partnerships and distribution channels and increase awareness among its large and growing base of small business customers.