The law stipulates that investment in municipal bonds is exempt from income tax. The law stipulates that investment in municipal bonds is exempt from income tax, which means that banks can reduce income tax by investing in municipal bonds. This provides a legal way for banks to avoid tax, because banks can buy municipal bonds instead of other high-tax investments, thus reducing their tax burden. And by investing in municipal bonds, banks can obtain stable interest income, which is usually exempt from income tax. Therefore, banks can use this investment method to increase profits and avoid the tax burden brought by other investment methods. Therefore, the prerequisite for banks to use securities investment for tax avoidance is that the law stipulates that investment in municipal bonds should be exempted from income tax.