Section 271F
If a person who is required to furnish a return of his income, as required under sub-section (1) of Sec 139 or by the provisos to that sub-section, fails to furnish such return before the end of the relevant assessment year, the Assessing Officer may direct that such person shall pay, by way of penalty, a sum of five thousand rupees..
Thus If you are filling the ITR for the AY 09-10 now, AO may impose penalty of Rs. 5000/- because last date was 31/03/10 for AY 09-10.