In India, the tax payable by an individual is based on his own assessment of income earned by him in a given Financial Year. When you file the return of income after paying your taxes, you are communicating to the Income Tax Department details like the various sources from which the income declared has been earned, TDS Credit availed and self-assessment tax paid if any. Only when you file the return of income the government assumes right over the taxes paid by you. Hence filing a return of income is a communication/ proof to the Government of the self-assessment of tax liability assumed and discharged by the individual.
Filling Income is the behavior towards your loyalty and discloser of income. It doesn’t mean you have to pay taxes. If you hide some of your other income, one day or other government standing on your doorstep with the notice, and at that time nobody can help you.