Here is a simple and easy IRS late payment penalty and interest calculator ! As you know ,IRS imposes tax penalty for underpayment of tax or for failure to file penalty for two distinct faults committed by the taxpayer under Internal Revenue Code. Both these penalties are explained elsewhere on this site, but readers will be happy to note that after much hardwork, a calculator for computing the penalty for filing tax return late and the penalty for not paying the tax has been created. Please send your feedback and suggestion on irstaxapp[at]gmail.com
IRS Penalty Calculator
First Time Penalty Abatement
If you failed to pay in time, it is not that you can not get waiver of such a penalty.Under the Internal Revenue Code, there are two ways to get that penalty for failure to pay removed. One is by explaining IRS the reasonable cause for failure to pay and the second is totally at discretion of IRS to all you a first-time penalty abatement under which you may qualify if certain conditions are fulfilled. Please read this post on first time penalty abatement.
Which provision of law handles failure to pay & file penalty?
Failure to file penalty is dealt under IRC § 6651(a)(1) where as law for imposing penalty for failure to pay tax as per your return is provided under IRC § 6651(a)(2).