While due diligence plays an important role in all aspects of tax practice, when a tax professional begins the process of assisting a taxpayer with a post-filing issue their first step in exercising due diligence should generally consist of a. Analyzing transcripts to learn more about the client's tax history and their status with the IRS b. conducing research on the type of notice or letter the client received c. interviewing the client to identify the issue d. interviewing the taxing authority to gain a thorough understanding of the problem