By not collecting the info (eg. a box to tick: "I confirm I am a tax resident of Canada"), Canada Revenue Agency cannot effectively enforce non-resident withholding tax collection, and, cannot easily verify when capital gains tax exemptions are wrongly taken (just tax residents of Canada can get the exemption). And, the tax residency info can be shared with the foreigner's home jurisdiction, to see if they honestly reported their foreign property holding and income. Want this fixed? Collect the info on tax residency from the parties at the time of the transaction, on the day of the transaction. If people do not have in hand two CRA Notices of Assessment covering the two previous tax years, deem the professionals around that transaction table liable for taxes owing until 'tax residence' is proven. That's the motivator.  You'll fix this quick.