Section 15
SEC. 15. The Collector of Internal Revenue shall assess all income taxes. In case of any failure to make and file a return or list within the time prescribed by law or by the Collector or other internal-revenue officer, the Collector of Internal Revenue shall add to the tax fifty per centum of its amount except that, when a return is voluntarily' and without notice from the Collector or other officer filed after such time and it is shown that the failure to file it was due to a reasonable cause and not to willful neglect, no such addition shall be made to the tax. In case a false or fraudulent return or list is willfully made, the Collector of Internal Revenue shall add to the tax one hundred per centum of its amount. The amount so added to any tax shall be collected at the same time and in the same manner and as part of the tax unless the tax has been paid before the discovery of the neglect, falsity, or fraud, in which case the amount so added shall be collected in the same manner as the tax.