26 CFR § 1.163-1 - Interest deduction in general.
(a) Except as otherwise provided in sections 264 to 267, inclusive, interest paid or accrued within the taxable year on indebtedness shall be allowed as a deduction in computing taxable income. For rules relating to interest on certain deferred payments, see section 483 and the regulations thereunder.
(b) Interest paid by the taxpayer on a mortgage upon real estate of which he is the legal or equitable owner, even though the taxpayer is not directly liable upon the bond or note secured by such mortgage, may be deducted as interest on his indebtedness. Pursuant to the provisions of section 163(c), any annual or periodic rental payment made by a taxpayer on or after January 1, 1962, under a redeemable ground rent, as defined in section 1055(c) and paragraph (b) of § 1.1055–1, is required to be treated as interest on an indebtedness secured by a mortgage and, accordingly, may be deducted by the taxpayer as interest on his indebtedness. Section 163(c) has no application in respect of any annual or periodic rental payment made prior to January 1, 1962, or pursuant to an arrangement which does not constitute a “redeemable ground rent” as defined in section 1055(c) and paragraph (b) of § 1.1055–1. Accordingly, annual or periodic payments of Pennsylvania ground rents made before, on, or after January 1, 1962, are deductible as interest if the ground rent is redeemable. An annual or periodic rental payment under a Maryland redeemable ground rent made prior to January 1, 1962, is deductible in accordance with the rules and regulations applicable at the time such payment was made. Any annual or periodic rental payment under a Maryland redeemable ground rent made by the taxpayer on or after January 1, 1962, is, pursuant to the provisions of section 163(c), treated as interest on an indebtedness secured by a mortgage and, accordingly, is deductible by the taxpayer as interest on his indebtedness. In any case where the ground rent is irredeemable, any annual or periodic ground rent payment shall be treated as rent and shall be deductible only to the extent that the payment constitutes a proper business expense. Amounts paid in redemption of a ground rent shall not be treated as interest. For treatment of redeemable ground rents and real property held subject to liabilities under redeemable ground rents, see section 1055 and the regulations thereunder.
(c) Interest calculated for costkeeping or other purposes on account of capital or surplus invested in the business which does not represent a charge arising under an interest-bearing obligation, is not an allowable deduction from gross income. Interest paid by a corporation on scrip dividends is an allowable deduction. So-called interest on preferred stock, which is in reality a dividend thereon, cannot be deducted in computing taxable income. (See, however, section 583.) In the case of banks and loan or trust companies, interest paid within the year on deposits, such as interest paid on moneys received for investment and secured by interest-bearing certificates of indebtedness issued by such bank or loan or trust company, may be deducted from gross income.
(d) To the extent of assistance payments made in respect of an indebtedness of the taxpayer during the taxable year by the Department of Housing and Urban Development under section 235 of the National Housing Act (12 U.S.C. 1715z), as amended, no deduction shall be allowed under section 163 and this section for interest paid or accrued with respect to such indebtedness. However, such payments shall not affect the amount of any deduction under any section of the Code other than section 163. The provisions of this paragraph shall apply to taxable years beginning after December 31, 1974.