Netfile error message says: Your spouse/partner's income for the year is required to properly calculate your tax return. If you don't enter it, when the CRA receives your spouse/partner's return you will be reassessed and you'll owe the difference in your refund or tax payable, plus interest. Your spouse/partner's income is required even if they passed away during the tax year.
When I click fix it takes me through these steps again - Information, Marital status, Nisga'a and Dependents.
Then repeat.
