I bought Ranbaxy few days before the merger and sold it off after Sunpharma get credited to my account.
What would be the tax implication on this?
Your cost price for holdings of Sunpharma will be the cost of Ranbaxy shares you held. Also the holding period will continue to be the same.
So if your Ranbaxy was long term gain, Sunpharma will continue to be long term gain too.
Check for section 47: http://www.incometaxindia.gov.in/Pages/acts/income-tax-act.aspx
No additional tax implication as such.