Promissory note with increased interest for late payment

You can do it. I cannot give you any case lawsbut it is well established fact that interest amount @x% p.a.as well as penal interest amount @y% p.a. can be added. Only thing is payment should not be conditional on happening of an event which may or may not happen, and should be a certain sum of money (Rs.A+Int @x%+Penal Int@y% IS a certain sum of money).

Promissory note cannot contain any conditional undertaking as defined in Sec.4 of N.I.Act