Under Federal law, there is a time restriction on how long the IRS has to collect unpaid taxes. This time restriction is most commonly known as the statute of limitations.
For most cases, the IRS has 3 years from the date the return was filed to audit a tax return and determine if additional tax is due. After the IRS determines that additional taxes are due, the IRS has 10 years to collect unpaid taxes. Most taxpayers can rest assured that after 3 years, it is highly unlikely that the IRS will attempt to audit them and assess additional taxes against them.
However, there are certain exceptions to these rules. If the IRS suspects fraud or criminal activity, the statute of limitations on auditing returns and attempting to collect unpaid taxes is then extended further based on the type of fraud
or crime involved.
The most important exception to the 3-year rule is that the IRS has up to 6 years to audit a return in situations where the IRS suspects the taxpayer underreported more than 25% of their gross income. The 3-year limitation is also extended to 6 years if a taxpayer underreports more than 25% of an estate or the amount of gifts given in a tax year. Even if you file a corrected amended return, that will not shorten the 6-year rule. False or fraudulent returns can be audited for up to 6 years.
If you suspect that the statute of limitations may have expired in your case, but you are still being contacted by the IRS, contact a tax attorney or other tax professional to determine whether it is lawful for the IRS to pursue collection from you.