How do I add my American spourse's social security number?

I am doing my taxes separate from my American spouse but I am still required to enter her SIN

Seniors and students

You only need to put some basic info and income for your spouse. 

So, you can use SIN 000 000 000 assuming they don't already have one. 

Estimated income in CAD and show the spouse as a non-resident. Do not claim spousal credit.

 

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