How eligibility periods work
Each Canada Recovery Benefit (CRB) eligibility period is a specific 2-week period. When you apply, you will receive a $1,000 ($900 after taxes withheld) payment for the period that you applied for.
The CRB does not renew automatically. You must apply for each period separately. You can apply for a maximum of 21 periods out of the total 26 periods available between September 27, 2020 and September 25, 2021. The 21 periods do not have to be taken consecutively. Extended
You may apply for benefits retroactively for any period up to 60 days after that period has ended.
Which periods you should apply for
You may apply for any period that you’re eligible for. If you meet all the eligibility criteria for the entire 2-week period, the earliest you can apply is the first Monday after the 2-week period has ended.
Each eligibility period is a 2-week period with a specific start and end date. You may start applying on the Monday after the 2-week period has ended.
If your situation continues, you must re-apply for another 2-week period.
You may apply for benefits retroactively for any period up to 60 days after that period has ended.
Your eligibility ends after 21 periods
Extended
The benefit is available between September 27, 2020 and September 25, 2021. You can no longer receive CRB payments after you have reached the maximum of 21 periods (42 weeks).
To confirm the number of periods that you have already received the CRB, you can review your application history in CRA My Account, under “COVID-19 Support Payment Application Details”.
source: https://www.canada.ca/en/revenue-agency/services/benefits/recovery-benefit/crb-periods-apply.html