Use 000 000 000 as a SIN# for now but I will encourage you to contact the CRA at 1-866-223-4403 to inquire about getting an ITN (Individual Tax Number) or TTN (Temporary Tax Number) for your non-resident dependant for tax purposes. The link below will provide you with the application form.
Footnote: You have indicated that you are using TurboTax Live Assist & Review – please refer to the links provided below to contact our team of Tax Experts if needed:
