Can I defer paying departure tax until I actually sell the assets?

Yes. You don't have to pay the tax on your deemed capital gains the moment you leave — the Income Tax Act lets you elect to defer payment until you actually dispose of the property later, whether that's next year or decades from now. The election has to be made with your return for the year you emigrate; it doesn't happen automatically just because you didn't pay.

The deferral covers the tax itself, but it isn't necessarily free of conditions: depending on the value involved, CRA may require you to post adequate security as a condition of deferring, which is covered separately. The gain itself is still calculated and reported for the departure year — deferring the payment doesn't mean deferring the reporting or the valuation.

This is one of the more useful tools available to someone leaving Canada with illiquid or hard-to-value assets, like private company shares, since it avoids forcing a tax bill on paper gains before you have cash from an actual sale. Because the election has real conditions attached, it's worth confirming eligibility and any security requirements with an advisor before you file your departure-year return.