First there is no need to panic when you receive a letter from income tax department .Stay calm and read thoroughly the entire notice if you can and make something out of that..Response to a notice depends on under what section of the Income tax act it is issued.Even under same section different types of notice can be issuedFor exampleNotice can be issued under 142(1) asking you to file returns electronically - you have to file a return In such case and you can give the reply electronically once you filed the returnNotice under same section can be issued asking you to present the documents as asked by the income tax officer- you have to present all the documents asked by ITO on date specified by him.Notice under section 143(1) can be issued when your return is processed and if there is outstanding tax payable - Then you can give reply electronically whether you accept it or notThus your response depends on actual purpose of noticeEither message me or you can very well take help of a Chartered accountant !!!