La. R.S. 47:161 — Income from sources partly within and partly without the State of Louisiana

A. Resident individuals. In the case of a resident individual, items of gross income, expenses, losses, and deductions, from whatever source received or incurred, not otherwise exempted by this Chapter, shall be included in the taxpayer's return and the amount of the tax shall be computed upon the entire income from whatever source derived; provided, that in the case of a taxpayer who, while a resident of another state, sells non-Louisiana property for a payment to be made over a period of years, the portion of such payment received after the taxpayer becomes a resident of this state shall not be included in taxable income.
B. Nonresident individuals, and corporations. In the case of a nonresident individual, or a corporation, items of gross income, expenses, losses and deductions, from whatever source received or incurred, not otherwise exempted by this chapter, shall be included in the taxpayer's return; but, for the purpose of this Chapter, the amount of tax shall be computed only upon the net income earned or derived from sources within the state, such net income to be computed as provided in Sub-part F of Part II of this Chapter.
C. Railroads incorporated in more than one state. Any railroad corporation incorporated under and by virtue of the laws of more than one state shall be taxed under this Chapter in the same manner as a foreign corporation.