Limits on Business Interest Deductions Under the Coronavirus Aid, Relief, and Economic Security (CARES) Act [March 27, 2020] [open pdf - 535KB]
From the Document: "Thin capitalization rules, broadly, limit the amount of debt that can generate deductible interest for the purpose of calculating taxable income. Limits on the tax deduction for business interest restrictions have been relaxed by the Coronavirus Aid, Relief, and Economic Security (CARES) Act (H.R. 748, as amended) providing economic stimulus and relief for taxpayers due to the expected slowdown of the economy because of the coronavirus pandemic. These restrictions, also referred to by their Internal Revenue Code Section 163(j), were expanded by the 2017 tax revision, P.L. 115-97."
CRS Insight, IN11287
Congressional Research Service: https://crsreports.congress.gov/