This article clarifies the capital gains taxation method with holding-period neutrality and tax revenue neutrality. Tax deferral is equivalent to an interest-free loan from the government and, to tax exemption for investment income. Understanding these relationships can lead to correct conclusions regarding the selection of capital gains tax methods. The Yield Based Method is most suitable from the viewpoint of holding-period neutrality, and the Interest Tax Method on tax deferral is most suitable from the viewpoint of tax revenue neutrality. As the Yield Based Method requests difficult calcuations for the taxpayer, I reached the conclusion that the Interest Tax Method should be adopted. This article describes an institutional design regarding the Interest Tax Method that adds credit risk premiums.