Service Canada updated their website to note the following:
No application is required .
The payment for seniors provides support through a one-time payment:
$300 for seniors eligible for the Old Age Security pension, and
an additional $200 for seniors eligible for the Guaranteed Income Supplement
The one-time payment for seniors is available to individuals who are eligible to receive the OAS or GIS in June 2020.
Individuals and their spouse or common-law partner will each receive $500 if both are receiving the GIS.
The one-time payment for seniors is non-taxable. You will receive the full amount (no withholdings). You will not receive a tax slip and you will not have to report this amount in your 2020 tax return.