Returns to be verified by oath.
Section 50
SEC. 50. Returns to be verified by oath. — The Collector of Internal Revenue or other internal-revenue officer shall require every return to be verified by the oath of the party rendering it. If the Collector or other internal-revenue officer has reason to believe that the amount of any income returned is understated, he shall give due notice to the person, making the return to show cause why the amount of income declared in the return should not be increased, and, upon proof of the amount understated, may increase the same accordingly. Such person may furnish sworn testimony to prove any relevant facts, and, if dissatisfied with the decision of an internal revenue officer, may appeal to the Collector of Internal Revenue for his decision under such rules of procedure as may be prescribed by regulations.