The final tax deadline for 2015 tax returns is October 17, 2016. This is the last day to electronically file those returns and also the last day to avoid a failure-to-file penalty. Failure-to-file penalties are typically up to 25% of the tax liability due and it’s it in addition to interest charges for paying late (which are usually a lot lower).
Ex: If your federal return shows a balance due of $1,000 and you do NOT file it by 10/17/16 (assuming you filed an extension by 4/15/16), you will be charged an additional penalty up to $250. This penalty can be avoid by simply filing the return on time.
Even if you don’t have the money to pay the taxes, you should always file your returns on time.