The California Society of Tax Consultants, Inc (CSTC), has been a nonprofit organization for the benefit of tax professionals throughout California since 1966 (formerly known as ISTC), and delivers quality education and unique member benefits. As a bookkeeper, accountant, Enrolled Agent, or CPA, you can take advantage of everything CSTC has to offer. Programs cover a wide spectrum of tax topics that are approved for CTEC, EA & CPA credit.