When the Knight Frank agency analyzed the main drivers of French Alps property purchases in 2019, one factor outweighed the traditional lure of the slopes and the growth of summertime activities in the mountains.

“It is not exactly glamorous, but the single biggest driver right now for choosing a French resort, rather than anywhere else is a simple one: a very nice tax break,” said Roddy Aris, the agency’s head of sales in the French Alps.

France normally imposes a 20 percent value-added tax on property purchases, but the tax break refunds it to buyers of newly built properties who are willing to rent them to vacationers. It also slashes the normal 7 percent transfer tax to 2 percent.

Mr. Aris said the tax rebate is available across France but it is mostly used in the Alps because it is aimed at supporting the tourism industry by encouraging owners to make more beds available.