GIS
The Service Canada page above includes resources that assist with completing tax returns at no cost.
For GIS:
“What is the Guaranteed Income Supplement? (GIS)
The Guaranteed Income Supplement (GIS) is a monthly benefit that is not taxable and income-based. It is available to Canadian residents aged 65 and over.
GIS benefits are renewed automatically each July, provided that an income tax return is filed by April 30.
For more information about the tax benefit for persons over 65 years old.