If the repayment of the dues are defaulted for more than 90 days, banks can classify that account as NPA.
If more than 80 % of the Principal plus interest thereon, was paid by the borrower, then bank cannot invoke provisions of SARFAESI Act to that account, as per Sec.31(j) of the Act, even if such dues are in many crores. In such cases, the only remedy to banks is filing suit (Original Application) before DRT.