Dear Amir,
The reason is in general, one rule by IRS to avoid penalties and interest, is if you pay 100% of prior years taxes either through withholding or by making timely estimated tax payments, you would generally not incur penalties and interest on additional amounts owed.

I would recommend that you pay 100% of prior years tax liability and I am sure you would not be assessed penalties and interest on additional liabilities when you file your tax return.

Regards
Tax Guru