The SEC noted the accounting firms' relationship with CBIZ via its alternative practice structure. The agency said MHM was negligent in lacking controls to detect transactions by its clients – which include more than 100 broker-dealer and investment fund clients – in CBIZ stock. The SEC says the firm also did not have written policies and procedures to deal with the independence issues involving its clients' stock trading. The SEC regards accounting firms and any partners in the alternative relationship to be covered by its independence rules.

MHM had informed Tradebot the firm believed that as long as it held less than 5 percent of CBIZ's stock, there were no problems. However, in a meeting in late October 2012, the SEC staff told the firm that a client's holding even one share of CBIZ stock would mean its independence was impaired.

Despite that warning, the day after the meeting the firm's engagement shareholder emailed Tradebot in answer to a September question about the issue, "I am assuming Tradebot has not become the beneficial owner of more than 5% of the CBIZ stock at one time, however, I would like to propose perhaps you put a limit on the number of shares to be acquired at any one time. Is that possible?" The SEC did not provide the names of any MHM accountants involved in the discussion.

And even though MHM was aware of the independence issue, it signed the engagement letter for the 2012 audit without resolving questions, the SEC said.