Changing Employment Terms: Do I Need a New Offer Letter or Just an Addendum?

If I am changing the terms and conditions of employment (e.g., leave policy) under the offer letter of the employee, do I have to issue a new offer letter or can I issue an addendum to the offer letter? Is there any notice period under law that I am required to give the employees?

Both ways are okay. A new offer letter or an addendum.

I will pass an internal memo as well as an email to all employees regarding the above.

What do you mean by giving notice period to the employee? What notice are you talking about? Let me know.

What I mean is, is there any stipulated notice period under any Indian statute that provides for a mandatory notice period, e.g., one month before the terms and conditions of service are varied.