So what are your chances of being audited?
There are two places to find the answers to this question. The first is found on the irs.gov website in statistics section and the second found in  IRS Publication 55B.
If you are a middle to upper middle class individual, you have about a 2.3% chance of being audited, which is down .3% from last year. If you are small corporation, your chances of being audited are 2.7% or lower. Larger corporations experienced an audit rate of approximately 14.5%. For S corporation and partnerships, the audit rate was .4%, the same as the previous year. 100% of corporations with total assets of $20 billion or more are audited.Let’s look at the numbers.
Individuals  Tax Audits:

• 1% of individual tax returns are audited
• Of those, 23% of those audits were conducted by IRS Field personnel
• 77% were mail correspondence audits

Percentage Breakouts:
Tax Returns between $100,000-$200,000 , audit chance            .7%
Tax Returns between $200,000-$500,000, audit chance             1.85%
Tax Returns between $1,000,000- $2,000,000 , audit chance    5.35%
IRS Number of Tax Returns filed for Corporations, Partnerships and S Corporations
2,245,168  regular C corporation returns
3,348,845  partnership returns
4,390,857  S corporation return were filed.
For all corporate returns other than Form 1120S, the overall percentage of returns audits was 1.3%
The audit rates for small corporations with total assets of:
$250,000 to $1 million,  1.3%,
$1–$5 million,                   1.8%
$5–10 million,                   2.7%,
The audit rates for large corporations,those totaling $10 Million and more
The overall audit rate was 14.5%
The audit rate for large corporations increased with the size of the entity.
Total assets of $10–$50 million       10.1%
Total assets of $50-$250 million       13.1%
Total assets     $250–$500 million   14.2% ;
Total Assets     $5–20 billion             48.7%
100% for those with $20 billion or more.
Penalties Assessed by the IRS

IRS assessed $26.387 million civil penalties against individual taxpayers,6672 and related other penalties
Top three penalties in percentage terms were :
54.71% for failure to pay,
28.67% for underpayment of estimated tax,
14.42% for delinquency.
Business

There were a total of 970,098 civil penalty assessments made by the IRS.