The infrastructure group had around 40 billion euros of consolidated net debt at the end of 2020, leading some analysts to expect part of the money would be used to clear borrowings.
However, the source, who declined to be named, said some of the funds would be used to help subsidiaries do deals and invest so they can generate cash to service and pay off their own debt.
For example, Spanish toll-road subsidiary Abertis, which alone had nearly 24 billion euros of debt last year, could be used as a platform to pull together other motorway concession businesses.
Atlantia's other subsidiaries include Rome airports operator AdR, Nice airport operator ACA and toll-road digital payments group Telepass.
Atlantia, controlled by the Benetton family, agreed this month to sell its 88% stake in motorway unit Autostrade per l'Italia in a deal that will end a dispute sparked by the deadly collapse in 2018 of a bridge in Genoa.
The deal is expected to complete in 6-8 months.
Last week, Atlantia said it would return to paying dividends and spend up to 2 billion euros on a share buyback, but was silent on debt.
The source said Atlantia Spa, the holding company at the top of the group, had already reduced its own net debt to 2.75 billion euros this year, from above 4 billion euros in 2020, and its earliest bond maturity was September 2023.
Consolidated debt is manageable since it is divided among subsidiaries and managed by each of them, the source added.
On Tuesday, credit rating agency Standard & Poor's upgraded Atlantia, Autostrade and Aeroporti di Roma (AdR) following the deal to sell Autostrade.
($1 = 0.8375 euros)
(Reporting by Francesca Landini; Editing by Mark Potter)
By Francesca Landini