[System.Xml.Serialization.XmlRootAttribute("root")]
        public class root
        {

            [System.Xml.Serialization.XmlAttribute("version")]
            public string version { get; set; }

            public class office
            {
                [System.Xml.Serialization.XmlAttribute("KPP")]
                public string KPP;
                [System.Xml.Serialization.XmlAttribute("INN")]
                public string INN;
                [System.Xml.Serialization.XmlAttribute("name")]
                public string name;
            }

            public office[] offices { get; set; }


            public void Save(string FileName)
            {
                XmlSerializerNamespaces ns = new XmlSerializerNamespaces();
                ns.Add(string.Empty, "");
                
                using (var writer = new System.IO.StreamWriter(FileName))
                {
                    var serializer = new XmlSerializer(this.GetType());
                    serializer.Serialize(writer, this, ns);
                    writer.Flush();
                }
            }
        }

<?xml version="1.0" encoding="UTF-8"?>

-<root version="1.2">


-<offices>

<office name=" туту фифрамама" INN="8888888888" KPP="12312321"/>

<office name=" туту фифрамама" INN="777777" KPP="12312321"/>

</offices>

</root>