What is a "Certificate/Letter of Incorporation" for an India visa?
A Certificate of Incorporation (or Letter of Incorporation) is a legal document that is issued by Ministry of Corporate Affairs to a company in India once they are successfully registered with them. This certificate is proof that the company is registered with the Registrar of Companies.
This letter is a general document that you should be able to request from your company in India. This does not need to be a traveler-specific letter.