The IRS has released (Rev. Rul. 2021-14) the Applicable Federal Rates under Sec. 1274(d) of the Internal Revenue Code for August 2021. These rates are used for various tax purposes, including minimum rates for loans.
There are rates for "short-term," "mid-term," and "long-term" instruments. Short-term covers demand loans and instruments extending up to three years. Mid-term covers loans cover loans and instruments of over three years up to nine years. Long-term covers loans and instruments with maturities longer than nine years.
The Section 382 long-term tax-exempt rate used to compute the loss carryforward limits for corporation ownership changes during August 2021 is 1.58%
The Section 7520 rate is used for valuing annuities and other planning techniques for estate and gift tax purposes. The current historically-low rates provide beneficial estate planning opportunities. Ava Archibald's Insight, Estate and Gift Tax—Are You Prepared for Changes?, is a great place to learn more.
Historical AFRs are available here.