If you are due a refund, there is no penalty as long as you file within 3 years.
You can request an extension to avoid penalties, which will give you until October to file (though it will not extend time to pay if you owe). You can file for an extension online. Please see more about filing extensions below:
https://ttlc.intuit.com/replies/3301811
Here is some information about penalties for filing late:
https://ttlc.intuit.com/replies/4159821
