Advent International and others are considering bids for the government's £1bn-plus-valued Land Registry.
City A.M. understands the buyout firm is one of a number of parties interested in the agency, which holds the titles for most of England and Wales’s land.
Delivering his Autumn Statement last November, chancellor George Osborne said the government would "consult on options to move operations of the Land Registry to the private sector from 2017".
And Sky News first reported today that Advent was drawing up plans to bid for the agency ahead of tomorrow's Budget, when further details could be announced.
Osborne is also expected to signal tomorrow his intention to sell a £16bn loan book that was once part of collapsed mortgage lender Bradford & Bingley.
Trade unions have previously warned the government against selling the Land Registry.
It emerged last November that the government had asked Rothschild, the investment bank, to consider options for selling Land Registry.
The agency has previously been valued at £1.2bn.
Ministers had already considered privatising part of the Land Registry, but in the coalition government former business secretary Vince Cable argued against a sell-off.
Advent International and the Treasury declined to comment.