If you have never previously subdivided or severed your parcel of vacant land from another that you owned and you subdivide the parcel into only two parts, the sale of either of those parts is exempt from the HST. If you subdivide the parcel into more than two parts, the sale of the parts is taxable. However, if you sell any part to a relative (or to a former spouse or common-law partner) for their personal use, that particular part is not taxable. The part sold to a relative would not be taxable even if the parcel of land had been previously severed from another parcel or even if the parcel is subdivided and severed into more than two parts.
The sale of the severed portion of vacant land would not be subject to GST/HST since it is not capital property used primarily (more than 50%) in a business and it is not being sold in the course of a business. However, if the land was subdivided into more than two parts, sales of the severed portions are not exempt unless the portion is sold to a relative (or to a former spouse or common-law partner) for their personal use.