The provisions of this Part shall apply to any person who is or may be engaged in any business, a portion of which is covered by or included in the various classes of business defined in R.S. 47:1003; but only upon the gross receipts derived from that portion of the business which is covered by or included in and not exempted by R.S. 47:1003 shall be subject to tax.
La. Revenue and Taxation § 47:1004