Hastert and his partners had sold parcels of land in Kendall County for a housing development project, allowing Hastert to take a large percentage of the sale's proceeds in the form of nearby land, the Chicago Tribune reports.
Hastert is the driving force behind the Prairie Parkway, a proposed federally-funded highway that runs nearby Hastert's newly acquired property, the newspaper said.
As part of the transaction, Hastert owns part of a 126-acre piece of property near the future housing project and highway, along with 275 acres in Eastman, Wis.
Any capital gains taxes accrued from an exchange of one property or business for another can be deferred under federal law.
Hastert's office denied he used his position to increase the property's value by supporting the funding of the new highway.
"It's too far away to have an effect," Hastert press secretary Ron Bonjean told the Tribune. "The speaker has bought land like every American has a right to.
"He is not benefiting from the parkway."