The IRS may adjust interest rates for various purposes at various times. For example, the rates for overpayments and underpayments of tax are adjusted quarterly.
Interest rates for Q3 in 2018. The interest rates on overpayments and underpayments are unchanged for the third quarter of 2018, which runs from through July 1, 2018 through September 30, 2018 (Rev Rul. 2018-18). The rates are:
- Noncorporate overpayments and underpayments: 5%
- Corporate underpayments: 5% generally but 7% for large corporate underpayments(generally underpayments exceeding $100,000)
- Corporate overpayments: 4% generally but 2.5% for corporate overpayments exceeding $10,000
Blended rate. Individuals with a below-market demand loan outstanding for all of 2018 can use a blended interest rate to determine what the lender must report as phantom interest income (imputed interest). The borrower may be able to deduct the imputed interest, depending on what the proceeds have been used for. For 2018, the blended rate is 2.03% (Rev. Rul. 2018-19).