Keep your number updated on your PAN card through the options offered by the government. To update your PAN card online, head to the official NSDL or UTIITSL website and navigate to "PAN card - Change/Correction in PAN Data." Enter your PAN details and select "Taxpayer" if applicable. They'll provide an online PAN application form. Simply update your mobile number in the designated section, upload scanned copies of your PAN card and ID proof, pay the processing fee, and submit the application. You'll receive a tracking number for future reference.