Hello Dariogs,

Maybe one possible approach to achieve this behavior is to handle ultraChart1_FillSceneGraph() event and include the code below:  

private void ultraChart1_FillSceneGraph(object sender, Infragistics.UltraChart.Shared.Events.FillSceneGraphEventArgs e)

{
    TextList.Clear();
    string IsAddedKey = null;
    foreach (Primitive pr in e.SceneGraph)
    {
        if (pr.Row != -1 && pr.Column != -1 && IsAddedKey != (pr.Row.ToString() + "-" + pr.Column.ToString()))
        {
            decimal tempPercent= (Convert.ToDecimal(pr.Value) / CalcSum(dt.Rows[pr.Row]))*100;
            Text textLable = new Text(new Point((int)((Infragistics.UltraChart.Core.Primitives.Path)(pr)).GraphicsPath.PathPoints[0].X, (int)((Infragistics.UltraChart.Core.Primitives.Path)(pr)).GraphicsPath.PathPoints[0].Y), tempPercent.ToString("0.00") + " %");
            textLable.PE.Fill = Color.Black;
            IsAddedKey = pr.Row.ToString() + "-" + pr.Column.ToString();
            TextList.Add(textLable);
        }
    }
    foreach (var item in TextList.Distinct()) 
        e.SceneGraph.Add(item);
}

Please take a look at the attached sample for more details. Please let me know if you have any questions.

Regards