There is no deduction available on interest on FDs/RDs. The entire interest income earned from these is liable to be taxed on accrual basis at the slab rate applicable.
Section 194A deals with a deduction of TDS on interest other than ‘interest on securities’. This could include Fixed Deposits & Loans and Advances other than banks. This TDS is deducted for resident individuals only.
There are different TDS rates described in different sections of the Income Tax Act, depending on the type and manner of the payment. TDS is deducted by estimating the likely tax amount on your income as per the slab rates currently prevailing for ...
Form15G/Form15H is only a declaration that no TDS should be deducted on your interest income since tax on your total income is nil. Interest income from fixed deposits, recurring deposits, and corporate bonds is always taxable.