I don't have any tax to pay. Do I still have to file ITR?
File a return, it is an important piece of paperwork that can come in handy later. Even if you have no tax to pay. It would take 5-10 mins at worst.
Filing an Income Tax Return (ITR), and paying taxes are two different things. A return filing is a declaration. Even if you're not eligible to pay taxes in a particular financial year; we recommend filing a return nonetheless.
An ITR is a piece of document that might need to be used in the event of a loan application, credit card application, or even visa interviews.
In fact, until you review your form 26AS, you won't know if there's an entity out there who's deducted TDS against your PAN. If so, you can claim a refund from IT dept. only via completing a return filing.
There's no harm in filing one, it clears up a lot of things and get those on the record.
These days, there are services like ClearTax, Quiko etc., that would let you file most common type of ITRs for free of cost. You can prepare and submit directly from these apps.
Other than this, you can also use official IT e-filing web portal, to file your ITR. While the UX of portal is not exactly a match for the other two services mentioned earlier; it already pre-populates data from 26AS and other sources in your ITR, so you're less likely to file returns with wrong values.