TDR (Ticket Deposit Receipt) is filed when you couldn't travel for valid reasons but the ticket wasn't auto-cancelled.
Valid reasons:
- Train cancelled by railways
- Train late by 3+ hours
- AC failed in AC coach
- Different class / lower class travel
- Coach not attached
- Did not travel
How to file TDR:
- Login to IRCTC.
- Go to My Account → My Transactions → File TDR.
- Select the booking and reason.
- Submit. Refund is processed in 60-90 days after IR's verification.
Time limits:
- Most cases: within 30 days of journey
- Train cancelled: within 90 days
Keep PNR + journey details handy.