The basic exemption limit is Rs 2.5 lakh under the old tax regime and Rs 4 lakh under the new tax regime for individuals under 60 years. This means that if your total income is at or below this amount, you don't have to file ITR. But, there are some exceptions, like if you pay a credit card bill over a certain limit, or travel abroad, then you must file an ITR regardless of your income level.
Another question that comes to mind is about special rate income like capital gains. For instance, if you are a student getting some pocket money from your parents or working part-time and decide to invest in listed equity shares but end up with a loss, you will need to file an ITR, even if your total income is below Rs 2.5 lakh (old regime) or Rs 4 lakh (new) regime if you want to carry-forward this loss to be set-off in future years. Otherwise, you generally don't have to file subject to certain conditions.
