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.
Loss from an unforeseen and sudden event that is deductible, subject to a 10% income floor and $100 reduction for personal losses.