private void btnMucThue_Click(object sender, EventArgs e)
 {
     FrmMucThue frm = new FrmMucThue();
     CreateTab(stcMenu, "Mức Thuế", "stiMucThue", "stcpMucThue", frm);
 }
        private void btnMucThue_Click(object sender, EventArgs e)
        {
            FrmMucThue frm = new FrmMucThue();

            CreateTab(stcMenu, "Mức Thuế", "stiMucThue", "stcpMucThue", frm);
        }