Section 6501(a) - The general statute of limitation within which the IRS must assess is 3 years from the due date of the return or the date the return is actually filed (state of California is 4 years);

Section 6501(e) – Contains the 6-year statute for the underreporting of income of more than 25%

Section 6501(c)(1), (2), & (3) provides for an unlimited statute for fraud, attempt to evade and failure to file.