1. How Can I Find Out Who Audits a Particular Company?
You can find the identity of the company's auditor in its annual report on Form 10-K. Look for the "Accountant's Report" under Item 8 of the Form 10-K.
To find a particular company's Form 10-K filings, use the Company Search for the SEC's EDGAR database. On the returned listing of filings for the company, enter “10-K” in the Filing Type box near the top of the page to filter for only Forms 10-K that have been filed.
2. Where can I find information about the changes to a company’s auditor?
Whenever a company hires a new auditor to certify its financial statements, it must announce that news on Form 8-K within four business days. Be sure to check any Item 4.01 of Form 8-K filings submitted after the company's most recent annual report to find out whether the company subsequently hired a new auditor.
...Excerpted from Researching Public Companies Through EDGAR: A Guide for Investors