The sale of Conrad Black's Toronto mansion has been put on hold after the Canada Revenue Agency placed liens against the property for $15-million in unpaid income taxes, according to documents obtained by The Globe and Mail.

The liens against the former media magnate's mansion at 26 Park Lane Circle in the upscale Bridle Path neighbourhood were registered on May 6.

The first lien said Mr. Black is indebted to the Canada Revenue Agency for unpaid income taxes totalling $12,307,717.15.

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The second lien is for unpaid income taxes of $2,771,196.84. The lien was filed by the Canada Revenue Agency on behalf of the U.S. Internal Revenue Service through the Canada-U.S. tax treaty, according to the documents.

No other details were provided in the documents. In an e-mail late Thursday, Mr. Black said: "It's nonsense, but a legal matter we'll work out judicially."

Mr. Black's home, which rests on 6.6 acres of property, was sold to an undisclosed buyer for $16.5-million, according to the Multiple Listing Service website. It was originally listed at $21.8-million.

Mr. Black and his wife, the writer Barbara Amiel-Black, planned on continuing to live in the home, which was sold as part of a lease-back deal.

The estate includes nine bed-rooms and 11 bathrooms along with a pool and spa. It was initially supposed to be auctioned off, but that was cancelled when a pre-emptive offer was made by a wealthy undisclosed buyer.

Mr. Black has three mortgages on the property amounting to $15.5-million. Two mortgages totalling $12-million are to the Hudson Bay Fund LP and the third mortgage that amounts to $3.5-million is with Hollinger Inc.

There is also a caution registered against title in favour of Hans G. Abromeit, which means the property cannot be sold without the consent of Mr. Abromeit.

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The 23,000-square-foot property was originally built by Mr. Black's father, George Montegu Black II, and had been in the family for 65 years. At one time, Mr. Black controlled Toronto-based Hollinger International, once one of the world's largest English-language empires whose flagship publications included Britain's Daily Telegraph, the Chicago Sun Times, the Jerusalem Post and the National Post.