In a 2011 speech, the Deputy Chief Accountant of the US Securities and Exchange Commission ("SEC") called for conformity among the business valuation credentialing organizations. He urged the business valuation community to create “a single set of qualifications with respect to education level and work experience, a continuing education curriculum, standards of practice and ethics, and a code of conduct.” He went on to say, “Valuation professionals [have a] lack of a unified identity. We accountants, for example, have a clearly defined professional identity. At last count, valuation professionals in the US can choose among five business valuation credentials available from four different organizations, each with its own set of criteria for attainment, yet none of which is actually required to count oneself among the ranks of the profession.” 
Despite these comments, there is still no mandatory requirement for business valuation appraisers to follow independently-mandated standards. Members of the American Society of Appraisers (“ASA”) are bound to follow the Congressionally-authorized Uniform Standards of Professional Appraisal Practice (“USPAP”); but nothing requires an appraiser to be an ASA member.
So, if you're trying to make sense of the various business appraiser credentials, see the schedule below for a breakdown of arguably the top three credentials and their requirements.
1] Prepared Remarks for the 2011 AICPA National Conference on Current SEC and PCAOB Developments, by Paul A. Beswick, Deputy Chief Accountant, U.S. Securities and Exchange Commission, Washington, D.C., December 5, 2011, https://www.sec.gov/news/speech/2011/spch120511pab.htm