The billionaire businessman has completed his purchase of chairman Freddy Shepherd's 28.01% stake to take control of the Premier League club.
He will now press ahead with plans to de-list the Magpies from the London Stock Exchange, as well as acquiring the 13% stake he now needs to force the remaining shareholders to sell.
A statement from Ashley's investment vehicle, St James Holdings Limited, on the club's official website: "SJHL now intends to procure the making of an application by Newcastle United to the London Stock Exchange for the cancellation of trading of Newcastle United shares and to the UKLA [UK Listing Association] for the cancellation of Newcastle's listing."
This is expected to take effect on July 18.
On reaching the 90% mark, the statement added SJHL planned to "acquire compulsorily" the remainder of the shares if necessary.