26 C.F.R. § 1.162-1 : Internal Revenue — INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY — INCOME TAX — INCOME TAXES —COMPUTATION OF TAXABLE INCOME —ITEMIZED DEDUCTIONS FOR INDIVIDUALS AND CORPORATIONS —1 - Business expenses

(a) In general. Business expenses deductible from gross income include the ordinary and necessary expenditures directly connected with or pertaining to the taxpayer's trade or business, except items which are used as the basis for a deduction or a credit under provisions of law other than section 162. The cost of goods purchased for resale, with proper adjustment for opening and closing inventories, is deducted from gross sales in computing gross income. See paragraph (a) of § 1.161-3. Among the items included in business expenses are management expenses, commissions (but see section 263 and the regulations thereunder), labor, supplies, incidental repairs, operating expenses of automobiles used in the trade or business, traveling expenses while away from home solely in the pursuit of a trade or business (see §1.162-2 ), advertising and other selling expenses, together with insurance premiums against fire, storm, theft, accident, or other similar losses in the case of a business, and rental for the use of business property. No such item shall be included in business expenses, however, to the extent that it is used by the taxpayer in computing the cost of property included in its inventory or used in determining the gain or loss basis of its plant, equipment, or other property. See section 1054 and the regulations thereunder. A deduction for an expense paid or incurred after December 30, 1969, which would otherwise be allowable under section 162 shall not be denied on the grounds that allowance of such deduction would frustrate a sharply defined public policy. See section 162(c), (f), and (g) and the regulations thereunder. The full amount of the allowable deduction for ordinary and necessary expenses in carrying on a business is deductible, even though such expenses exceed the gross income derived during the taxable year from such business. In the case of any sports program to which section 114 (relating to sports programs conducted for the American National Red Cross) applies, expenses described in section 114(a)(2) shall be allowable as deductions under section 162(a) only to the extent that such expenses exceed the amount excluded from gross income under section 114(a).
(b) Cross references.
(1) For charitable contributions by individuals and corporations not deductible under section 162, see §1.162-15.
(2) For items not deductible, see sections 261-276, inclusive, and the regulations thereunder.
(3) For research and experimental expenditures, see section 174 and regulations thereunder.
(4) For soil and water conservation expenditures, see section 175 and regulations thereunder.
(5) For expenditures attributable to grant or loan by United States for encouragement of exploration for, or development or mining of, critical and strategic minerals or metals, see section 621 and regulations thereunder.
(6) For treatment of certain rental payments with respect to public utility property, see section 167(1) and § 1.167(1)-3.
(7) For limitations on the deductibility of miscellaneous itemized deductions, see section 67 and §§1.67-1T through 1.67-4T.
(8) For the timing of deductions with respect to notional principal contracts. see §1.446-3.

26 C.F.R. §1.162-1

T.D. 6500, 25 FR 11402, 11/26/1960, as amended by T.D. 6690, 28 FR 12253, 11/19/1963; T.D. 6996, 34 FR 835, 1/18/1969; T.D. 7315, 39 FR 20203, 6/7/1974; T.D. 7345, 40 FR 7437, 2/20/1975; T.D. 8189, 53 FR 9881, 3/28/1988; T.D. 8491, 58 FR 53128, 10/14/1993