The Guaranteed Income Supplement (GIS) is a financial assistance program in Canada designed to provide additional income to low-income seniors. It is available to individuals who receive the Old Age Security (OAS) pension and have limited financial resources. The GIS helps ensure that seniors can maintain a basic standard of living. Eligibility for the GIS is based on income and marital status, and the amount received varies depending on these factors. Seniors must apply for the GIS through Service Canada, and it is reviewed annually to adjust for changes in income and living circumstances.