Hi, under 234A, simple interest of 1% will be calculated from the due date of filing to the date of filing the return after due date on the amount of tax payable by the assessee. also, as per 234F for filing after due date rs 5000 payable as fee for late filing till 31st Dec of the AY. After that rs. 10000 payable. but, the amount is restricted to rs. 1000 if the income of the assessee is below rs.500000