The last date to Opt-in or Opt-out of the QRMP scheme for the quarter April-June 21′ is April 30, 2021′.
Taxpayers who want to file Returns on a Quarterly or Monthly basis may exercise their option before the due date. After 30th April there will be no change in Return filing frequency for the quarter.
To opt in for the scheme → Login > Services > Returns > Opt-in for quarterly return
Source from: https://twitter.com/Infosys_GSTN/status/1387691196760268804