IRS interest rates are unchanged for the fourth quarter of 2013 (October 1, 2013, through December 31, 2013). These are the rates changed on underpayments and overpayments:
The 3% rate applies to underpayments of estimated taxes by individuals. All of these rates have held steady since October 1, 2011.
Source: Rev. Rul. 2013-16
A tax technique for receiving a refund of back taxes by applying a deduction or credit from a current tax year to a prior tax year. For example, a business net operating loss may be carried back for two years.