How banks compute the penalty
- Look up the FD card rate that applied for the tenure you actually held (e.g. 2-year rate if you held it 2 years).
- Subtract the premature-withdrawal penalty (typically 0.5%–1.0%).
- Recompute interest from day 1 at that effective rate.
- Pay you principal + recomputed interest.
If the card rate for the held tenure is higher than the contracted rate, the contracted rate prevails (you never get more than what was promised).