How have courts dealt with the unforeseen tax consequences of a sale of shares?

In McLeod v. Canada, supra, the unforeseen tax consequences of a sale of shares was held not to be a mistake which rendered the subject matter of a contract essentially and radically different from what was believed to exist. In that case, the appellants had been advised that there would be no adverse tax consequences if they sold the shares of their company to their children. However, the transaction was assessed such that the appellants were liable for a deemed dividend. The court found that the transaction was actually what the parties thought it was; a sale of shares over a term of years, and their advisors’ failure to warn about the tax consequences was wholly collateral to the contract.