The only time you are asked about your spouse's AGI if filing separately should be the premium tax credit. You can only claim the PTC when married filing separately if you are separated due to abuse or spousal abandonment. See here,
https://www.irs.gov/affordable-care-act/individuals-and-families/questions-and-answers-on-the-premiu...
Are you asking about a Canadian tax return? The Canadian support site is here,
https://turbotax.community.intuit.ca/community/turbotax-support/help/03/en-ca
