PN means a paper with a writing which has a promise. But it does not mean that we write "I owe You" and it becomes a PN.
PN is always in writing
PN has an unconditional undertaking called promise
The promise is to pay money
The money has to be paid to the certain person.
Please note that when a person issues a promissory note, he/ she would have to stamp it as per the Indian Stamp Act and normally a revenue stamp is affixed on the PN signed by the promissory.
The PN can be Demand Promissory Note or Usance Promissory Note. Demand Promissory Note has to be paid immediately on demand and Usance Promissory Note has to be paid after certain time period.
There are two parties in the PN. The maker is who promises to pay and the payee is who is promised to pay.
Is a currency Note a promissory note?
The currency Notes bear the following note signed by Governor Reserve Bank of India (for more than ` 1) and Finance Secretary (` 1) :
I promise to pay the bearer a sum of ________Rupee/ Rupees.
However , Currency notes are money and they don't fulfill the conditions of the PN. The currency is excluded from NI act and governed by Indian Currency Act. So Currency notes are Not promissory Notes.