submission of form 15g

Hi sir,

My brother had made an fd which is matured after 8yrs.His earning is below basic limit,now the bank is ready to deduct tds asking pan from my brother.If at all the bank wants to deduct tds will it deduct on entire matured amt or (on difrnc b/w matured amt & principle amt).can he submit form 15g even after deduction of tds.Thanks in advance...