The interest rates on overpayments and underpayments are unchanged for the first quarter of 2018, which runs through March 31, 2018 (Rev Rul. 2017-25). The rates are:
The 4% rate is used to figure estimated tax penalties for individuals.
These rates have remained constant since April 1, 2016. However, as the Federal Reserve raises rates, it is expected that IRS interest rates will be increased in the future.
A retirement account to which up to $4,000 (or $5,000 if you are 50 or over) may be contributed for 2007, but deductions for the contribution are restricted if you are covered by a company retirement plan. Earnings accumulate tax free.