Visit the Income Tax e-filing portal: https://www.incometaxindiaefiling.gov.in/
Click on the "Link Aadhaar" option under the "Quick Links" section on the left-hand side of the page.
Enter your PAN and Aadhaar number in the respective fields.
Enter your name as mentioned on your Aadhaar card.
Verify the captcha code and click on the "Link Aadhaar" button.
If the details entered by you match with the details in the Aadhaar database, your Aadhaar card will be linked with your PAN card.
Alternatively, you can also link your Aadhaar card with your PAN card by sending an SMS to 567678 or 56161. The format for the SMS is:
UIDPAN<SPACE><12 digit Aadhaar number><SPACE><10 digit PAN number>
For example, if your Aadhaar number is 123456789012 and your PAN number is ABCDE1234F, the SMS should be sent in the following format: UIDPAN 123456789012 ABCDE1234F.
Once you have successfully linked your Aadhaar card with your PAN card, you will receive a confirmation message on your registered mobile number and email address.