The Indus Script
Possibly the earliest form of a writing system in the Indian subcontinent is the Indus Script, and the Indus Valley civilization developed it. However, from what I understand and have read on many different occasions, the origin of this script is not fully understood, and much of it remains undeciphered.
What is known as the Harappan phase dates to around 3500 to 2700 B.C., and this is where there are examples of pottery having Indus Script signs.
My research found that the writing system wasn’t fully developed until around 2600-1900 B.C.