December 31, 2025, is a significant deadline for taxpayers and central government employees, marking the end of several financial and administrative tasks. Key deadlines include filing revised and belated Income Tax Returns (ITRs) for the assessment year 2025-26 and linking Aadhaar cards with PAN cards. Failure to link PAN with Aadhaar by this date may render the PAN inoperative from January 1, 2026, potentially disrupting tax filings and refunds.