What is a Section 116 clearance certificate and why does a non-resident seller need one to close in Ontario?

A clearance certificate is a document a non-resident seller applies for from the Canada Revenue Agency, under the Income Tax Act's rules for non-residents disposing of Canadian real property, confirming that the seller's tax obligations on the sale have been addressed or otherwise properly secured. It matters at closing because of the withholding rule discussed in a related question: without a certificate, the buyer is generally required to withhold based on the full purchase price, whereas a certificate can let the withholding be calculated on the smaller, actual net gain instead.

For a seller, obtaining the certificate is really about controlling how much of the sale proceeds get tied up in withholding at closing rather than avoiding Canadian tax altogether - the underlying tax obligation itself does not disappear, but the certificate helps make sure withholding reflects reality rather than the full sale price. Because the process takes time and involves the CRA directly, waiting until shortly before closing to start it can create real problems, addressed further in a related question.

Start the clearance certificate application as early as possible once a sale is anticipated, working closely with your lawyer and a tax advisor.