Is it necessary to show my income from my last employer in my ITR if?
Look it is necessary to show everything as well as nothing. As per act,you have to show your income from all the sources even if your income is below taxable limit.However if you don't show any such income then once you get caught ,it will be a huge penalty and you will charged for misrepresenting your income and you will be ending up paying a much higher amount of tax and penalty that you would have been originally liable. So why not show your original income and post nil tax instead!