diff --git a/caimira/apps/calculator/static/js/co2_form.js b/caimira/apps/calculator/static/js/co2_form.js
index bf9751bd..39596a61 100644
--- a/caimira/apps/calculator/static/js/co2_form.js
+++ b/caimira/apps/calculator/static/js/co2_form.js
@@ -28,9 +28,11 @@ const CO2_data_form = [
 	clearFittingResultComponent();
 	const files = document.getElementById("file_upload").files;
 	if (files.length === 0) {
-	  alert("Please choose any file...");
+		$("#upload-error").show();
 	  return;
-	}
+	} else {
+		$("#upload-error").hide();
+	};
 	const file = files[0];
 	const extension = file.name.substring(file.name.lastIndexOf(".")).toUpperCase();
 	extension === ".XLS" || extension === ".XLSX"
@@ -120,6 +122,7 @@ const CO2_data_form = [
 	}
 	if (submit) {
 	  $($(obj).data('target')).modal('show');
+	  $("#upload-error").hide();
 	}
 	return submit;
   }  
@@ -242,6 +245,7 @@ function submitFittingAlgorithm(url) {
 	$('#fitting_ventilation_states').val('');
 	$('span.error_text').remove();
 	$('#DIVCO2_fitting_result, #CO2_input_data_div').hide();
+	$('#DIVCO2_fitting_to_submit').hide();
 	$('#CO2_data_plot').attr('src', '');
   
 	// Update the ventilation scheme components
diff --git a/caimira/apps/templates/base/calculator.form.html.j2 b/caimira/apps/templates/base/calculator.form.html.j2
index c12cb6c0..4516d187 100644
--- a/caimira/apps/templates/base/calculator.form.html.j2
+++ b/caimira/apps/templates/base/calculator.form.html.j2
@@ -297,7 +297,6 @@
               </div>
             </div>
           </div>
-
       </div>
       <br/>
       
@@ -331,7 +330,7 @@
               <!-- Input element to upload an excel file -->
               <input type="file" id="file_upload" />
               <button type="button" class="btn btn-primary btn-sm" onclick="uploadFile('{{ get_calculator_url() }}/co2-fit/plot');">Upload</button>  
-              <br>
+              <div id="upload-error" class="mb-0 mt-2 alert alert-danger" style="display: none" role="alert">Please choose any file...</div>
               <br>
               <!-- table to display the excel data -->
               <table id="display_excel_data" border="1" style="width: 70%; margin-left: auto; margin-right: auto"></table>