How far back can the IRS send a CP 2000 letter?

[TomD8]

The tax code gives the IRS three years to audit your tax return and 10 years to collect any tax you owe.

Additionally:

• The IRS has six years from the date a return is filed to audit a tax return and to assess additional tax if the taxpayer omits income that amounts to more than 25 percent of that which was reported on the tax return.
• The IRS also has six years to audit a tax return and assess additional tax on income related to undisclosed foreign financial assets if the omitted income is more than $5,000.
• The statute of limitations on audits and assessing additional tax remains open indefinitely if the taxpayer files a false or fraudulent tax return.