A grantor retained annuity trust is a creature of US gift and estate tax. Canada taxes on deemed disposition at death rather than levying an estate tax, so the problem a GRAT solves does not exist here in the same form, and the mechanism has no Canadian equivalent.

The nearest Canadian tool is an estate freeze: you exchange your common shares for fixed-value preferred shares, and new common shares — which carry all future growth — are issued to a family trust. Your tax liability at death is frozen at today's value. It rhymes with the GRAT in purpose and shares none of its mechanics, so do not reason from the American version.