Do I Have to Repay the GST/HST New Housing Rebate in Canada If I Sell the Home Soon After Buying?

This answer covers Canadian federal tax law, which applies in every province.

It depends on whether you were entitled to the rebate in the first place, not just on how quickly you sold. An individual who receives a rebate they were not entitled to must repay it.

The key test is your intent. The intent to use the house as your or a relation's primary place of residence must be evident at the outset of buying, building or substantially renovating. A cottage, an investment property, or a house you plan to use on a more distant occasion such as retirement does not qualify. The statute does not set a number of days to move in. If a builder paid or credited a rebate it knew or ought to have known you were not entitled to, you and the builder are jointly and severally liable to repay it.

If you built the home yourself, a sale is generally exempt if you are not a builder for GST/HST purposes and claimed no input tax credits, but it may be taxable if you had a primary or secondary intention to sell. Because your facts decide the answer, speak with a lawyer or accountant before you list or move out.