Here is what you have the right to know:

1. When the IRS has finished an audit.
2. The maximum amount of time you have to challenge the IRS’ position.
3. How long the IRS can audit a particular tax year
4. How long the IRS can collect on a tax debt.
5. The IRS generally has 3 years to assess any additional tax from the date you file a return.
6. Exceptions to the 3 years include filing a false or fraudulent return. The IRS is then able to assess tax for that tax year at any time.
7. The IRS generally has 10 years from the date of assessment to collect any unpaid tax balance.
8. The above 10-year period cannot be extended unless you as the taxpayer agree as part of an installment agreement or a court judgment allows for it.
9. This 10-year period can be suspended at times which include when a taxpayer files for bankruptcy, there is an ongoing collection due process proceeding and the taxpayer is before the US Tax Court.
10. An IRS statutory notice of deficiency lets a taxpayer know how much the IRS is proposing additional tax due.  This notice is to include the deadline for filing a petition with the tax court and it cannot be changed.
11. A taxpayer is supposed to be subject to no more than one audit per tax year and the IRS will only reaudit in certain circumstances which include when a taxpayer files a fraudulent return.

See,  IRS Taxpayer Bill of Rights.

 More Information:
Publication 1, Your Rights as a Taxpayer
Taxpayer Advocate Service