When you sell your principal residence or when you are considered to have sold it, usually you do not have to report the sale on your income tax and benefit return and you do not have to pay tax on any gain from the sale. This is the case if you are eligible for the full income tax exemption (principal residence exemption) because the property was your principal residence for every year you owned it.

Starting with the 2016 tax year, generally due by late April 2017, you will be required to report basic information (date of acquisition, proceeds of disposition and description of the property) on your income tax and benefit return when you sell your principal residence to claim the full principal residence exemption.

如果你改变用途，从税务角度上讲，相当于卖出，也就是“when you are considered to have sold it”。从2016年以后，你就要报basic information (date of acquisition, proceeds of disposition and description of the property)，但不用交税。从改变用途那天以后的capital gain是要交税的。所以要有改变用途那天的市场价，以此作为proceeds of disposition去报税和capital gain的起点。

我不知道你问你会计师的原问题和他回答的原话，估计有什么双方理解上的不一样。比如，你问要不要交税，他说不要。但不交税不等于不申报。