IRCC allows 60 days to submit the complete PR application after ITA (Invitation to apply) is issued to candidates in their online express entry profiles. But due to unprecedented times because of COVID-19, now IRCC is giving candidates 90 days to submit their PR applications along with supporting documents.
This is just a temporary measure so that candidates get enough time to collect the documents they need. If more time is required or someone is not able to submit required documents on time such as biometrics, passports etc , they can contact IRCC via Webform.