Importance of why you should timely file....

When do you owe a penalty to the IRS? If you don't file your taxes when the IRS owes you money, you won't be penalized financially. However, you need to file to obtain any refund. You have until 2021 to file your return and still claim a refund on your 2017 taxes. 
If you owe money to the IRS, you need to file your tax returns and pay what you owe by April 17, 2018 for the 2017 tax year. If you can't file by the deadline, you can request an extension until October 15, 2018.
An extension on your time to file is not an extension on the time you have to pay what you owe. If you get a filing extension but don't pay your tax bill by April 18, you'll still face late-payment penalties in most cases. Penalties for failing to file your taxes and paying your taxes late are both charged in addition to any interest you owe on your unpaid tax balance.
The failure-to-file penalty is much higher. If you don't file your taxes when you owe money, you could be hit with not one, but two penalties imposed by the IRS: failure to file and failure to pay.

• The failure-to-file penalty is equal to 5% of the taxes you owe for each part of a month you're late, up to a maximum of 25% of unpaid taxes. This means if you're two days late with filing and you owe $1,000 in taxes, you could be hit with a $50 penalty. If you're more than 60 days late, the minimum penalty is the lesser of $205 or 100% of the unpaid tax.
• The failure-to-pay penalty is .5% of unpaid taxes for each part of a month you're late, up to 25% of unpaid taxes due. This is the penalty you're charged if you file on time but don't pay what you owe. However, if you request an extension to file and pay at least 90% of taxes owed, you may not be charged any failure-to-pay penalties as long as you pay the remaining 10% by the extended due date.
• The combined penalty for failure to pay and failure to file is 5% of unpaid taxes for any month in which you owe both penalties.

A quick glance at these penalties shows why it's so important that you file your taxes on time, even if you can't pay on time. In most cases, the failure-to-file penalty is 10 times greater than the failure-to-pay penalty.