Aadhar number and PAN number are two essential identity proofs for any citizen of India. They hold their own good usage at a lot of places individually. A PAN is more related to financial transactions whereas Aadhar is a general identity proof. 2017 onward, it has become mandatory to link Aadhar and PAN card. If you wish to file an ITR and get the returns from the government of
India, it is mandatory to link the two numbers. Although you can file ITR without linking Aadhar with PAN card but the returns would only be processed once the linking is done.
The linking can be done online on the e-filing official web page. This facility is available for both the users- ones whose name matches in both the documents as well as for the ones whose does not.

Linking Aadhar and pan online
The online linking of Aadhar and PAN can be done in two ways- without logging into the account and by logging into the account.

A) Without logging into the account (2-step process)
The income tax department has highly simplified linking Aadhar to PAN without logging into an account by simple two steps. It saves a lot of time and effort of the user.
Follow these two steps to link your Aadhar with PAN card;
Step 1: Visit the official e-filing page at www.incometaxefiling.gov.in and click on the link saying- ‘LINK AADHAR’.
Step 2: fill in the asked details like
• NAME (As on Aadhar card)
Submit these details and wait for verification from UIDAI. Once verified, UIDAI will confirm the linking.
In case there is a minor difference in name in the two cards, Aadhar OTP will be generated on the registered mobile number. In this case, the gender and date of birth should be exactly the same on both the documents. If the mismatch is major, the authentication and linking will fail. The user will be redirected to another page where he/she will be asked to change the name in either Aadhar or PAN database.

B) By logging into the account (4-step process)
Step 1: register or login to your e-filing account of the income tax department portal using your login ID and password. Date of birth is also required as a security check while you log in.
Step 2: once you login to your account, an automatic pop-up will be generated asking you to link your Aadhar with PAN. In case there is no pop-up, got to ‘Profile Settings’ on the top and then click ‘Link Aadhar’.
Step 3: verify your mentioned details already furnished during registering for Aadhar like Name, DOB, Gender, etc.
Step 4: once the details match, key in your Aadhar number and captcha image code flashed on the screen. Click on ‘Link Now’ tab.
On successful linking, a pop-up message will be promoted on your screen regarding the same.

Linking PAN and Aadhar can also be done through SMS facility. You can do so by sending a message to numbers- 567678 or 56161.

Use the following format:
UIDPAN<12-DIGIT AADHAR NUMBER><10-DIGIT PAN > and send it to 567678 or 56161.
For example, the SMS body will be like UIDPAN 131415161718 QWERT9876Y