You may be great with numbers, but unless your uncle runs the department, you're going to need some qualifications to get your foot in the door.
The most common qualification for becoming an IRS Auditor is a bachelor's degree in some discipline related to accounting. Having coursework in business or law can also be extremely helpful.
Combine your bachelor's degree with a certification in Public Accounting and you are bound to get the gig.
Once hired, most positions will require up to a year of on-the-job training to assure you are current on all new tax codes and laws. This type of job experience will make you much more desirable in the future should you need to look for a similar job elsewhere.