Hi dilip5555,
Notes in circulation cannot be imported. It is illegal. However, if the notes are - 1) Defective 2) Commemorative or 3) Old and out of circulation, then you can prove that it is for collection purpose. In this case, the custom duty would be applicable as per the invoice amount based on the HS codes. You can ask the seller to send a PayPal invoice and present it to the custom office for the verification purpose. In most of the cases, there is no duty on collectible notes.
Kind Regards,
MB