To date, more than 1,800 public accounting firms have registered with the PCAOB, including approximately 830 firms based outside the United States. Firms with more than 100 public company audit clients must be inspected annually; firms with one to 100 public company audit clients must be inspected at least once every three years. The PCAOB's budget is subject to approval by the US Securities and Exchange Commission.
Press Release (PDF 59k).