According to Section 139AA in the Income Tax Act (2017), individuals have to link their Permanent Account Number (PAN) and Aadhaar numbers. The deadline is March 31, 2021. If they are not, PAN will be considered invalid to use.
Until 2017, income tax could be e-filed without the PAN-Aadhaar link. Earlier, the deadline to link the both was August 31, 2017, and then kept getting postponed until the central government put a stop. Even though the I-T returns can be filed, the returns cannot be processed without the linkage.
This is the eighth time in a row that the government has extended