Uncle Sam nailed Nelly with a $2,412,283 federal tax lien in August.
The tab is so big, the IRS could start seizing his assets and property.
He's also has state tax trouble.
Earlier this year, the Missouri Department of Revenue said the St. Louis rapper owed $149,511 in unpaid state taxes from 2013.
He originally owed a mere $113,533, but that was before interest.
Sources close to Nelly told TMZ he's already working with the tax authorities to resolve the issues.