15-30-2102. Construction of net income. For the purpose of raising revenue, the net income required to be shown on returns under this chapter and taken as the basis for determining the tax hereunder shall not be classified or held or construed to be property. All income except what has been expressly exempted under the provisions of this chapter and income not permitted to be taxed under the constitution of this state or the constitution or laws of the United States shall be included and considered in determining the net income of taxpayers within the provision of this chapter.