The Nottinghamshire businessman has changed his Twitter biography to 'Notts County owner and chairman' and is likely to be the Magpies' new leader before the visit of Mansfield on Saturday.
Hardy also tweeted: "Finally got there guys, thank you for all your tremendous support! Now let's get this Club back where it belongs! New World starts today!"
A deal had been in danger because of an outstanding seven-figure loan to the estate of Haydn Green, who helped saved the club from extinction in 2003, and talks were ongoing over who paid it.
The club are also the subject of a winding-up petition brought by HM Revenue & Customs and have until February 6 to settle any outstanding debts.
Hardy, owner of Nottinghamshire Golf and Country Club, arrives with the Magpies having sacked manager John Sheridan on January 2 after a run of nine straight defeats.
Caretaker manager Alan Smith took charge of their 4-1 loss at Morecambe on Saturday and County are 22nd in League Two.