Non-deductibility of expenditures prevents deductions for income outside total income and unlawful or previously claimed expenses.

Non-deductibility rules exclude expenditures attributable to income outside total income, amounts previously deducted, expenditures for unlawful or prohibited purposes, and provisions for liabilities that remain unascertained at year end; specified cross-referenced expenditures are also excluded. The Code bars claiming the same deduction under multiple provisions and provides that these disallowance rules govern despite any contrary Chapter provisions.

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