The IRS statute of limitations to revisit, review or analyze a tax return is generally three years for an audit.
For very large understatements of income (25% or more) or unreported offshore income and assets, the statute is 6 years. It is not clear what statute of limitation applies to carryover items. The answer would depend on what you call "substantial" and the overall picture of your tax return. We would suggest discussing this issue with a professional handling your return.
