@ jraju.. you still have misunderstandings... let me help you clear it..
form 15g/h is not a declaration where we commit to pay tax separately. it is a declaration that our income including intt on FD will be below taxable limit and hence no TDS should be deducted. however, if after submitting form 15g/h to bank, our income exceeds taxable limit then we are required to pay taxes accordingly.
FD intt is never exempted from tax. section 194A gives a limit of 10000 that TDS is not be deducted upto this amt. this does not mean that if intt is below 10000 then its exempt. it is still taxable and the person has to pay tax, but bank will not be under obligation to deduct TDS on this amt.
sec 234A charges penal intt @ 1% p.m. for delay in filing of return.
sec 234B charges penal intt @ 1% p.m. for payment of advance tax liability less than 90%
sec 234C charges penal intt @ 1% p.m. for deferment of advance tax liability.