Generally the IRS audit process starts with an information document request. The auditor requests information surrounding their examination of whatever tax return is under audit . The taxpayer will then gather that information and will meet with the auditor to go over the results of that information. A lot of times by looking at the auditor's document request you can tell why the return got audited. Most audits will focus either on the income side of things or on the deduction side of things. Occasionally they will focus on both. In any event the taxpayer will sit down, then will meet with the auditor or they'll have the representative meet with the auditor and the auditor will go through the substantiation with the taxpayer and/or their representatives. At the end of the review of the substantiation, the auditor will make adjustments based on things that they feel are they are owing to the government and they will prepare a report and present it to the taxpayer. If the taxpayer agrees with the report then the audit is over. If the taxpayer or the representative disagree with the report they see may submit additional documentation and/or work to clarify things in the audit report. If the auditor and the taxpayer ultimately cannot agree, then the case goes to Appeals where the taxpayer can further challenge the audit. That's how the IRS audit process works.