Index: MuiscOrganizationSystem/settings.py
===================================================================
--- MuiscOrganizationSystem/settings.py	(revision d0b1ea74bdcbf92413abee6cdf506065f9e4a08e)
+++ MuiscOrganizationSystem/settings.py	(revision d4c80c07957ce76ec98052794bc5a3da8d5f08d0)
@@ -130,2 +130,4 @@
 
 DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"
+
+DATA_UPLOAD_MAX_NUMBER_FIELDS = 10000
Index: music/urls.py
===================================================================
--- music/urls.py	(revision d0b1ea74bdcbf92413abee6cdf506065f9e4a08e)
+++ music/urls.py	(revision d4c80c07957ce76ec98052794bc5a3da8d5f08d0)
@@ -24,4 +24,5 @@
     path('employee/batch-update-reports-to/', views.batch_update_reports_to, name='batch_update_reports_to'),
     path('playlists/add-tracks/', views.add_tracks_to_playlist, name='add_tracks_to_playlist'),
+    path('invoices/add-lines/', views.add_invoice_lines_to_invoice, name='add_invoice_lines_to_invoice'),
 
 ]
Index: music/views.py
===================================================================
--- music/views.py	(revision d0b1ea74bdcbf92413abee6cdf506065f9e4a08e)
+++ music/views.py	(revision d4c80c07957ce76ec98052794bc5a3da8d5f08d0)
@@ -18,6 +18,8 @@
     return render(request, 'home.html')
 
+
 def redirect_to_home(request, exception):
     return redirect('home_page')
+
 
 ## LIST OF ALL ##
@@ -145,4 +147,5 @@
         'selected_customer_id': selected_customer_id,
     })
+
 
 def most_popular_artist_per_customer_per_genre(request):
@@ -244,11 +247,14 @@
     })
 
+
 from django.shortcuts import render, redirect
 from music.models import Employee
 from django.contrib import messages
 
+
 def batch_update_reports_to(request):
     selected_manager_id = request.POST.get('manager_id') or request.GET.get('manager_id')
-    employees = Employee.objects.exclude(employee_id=selected_manager_id) if selected_manager_id else Employee.objects.all()
+    employees = Employee.objects.exclude(
+        employee_id=selected_manager_id) if selected_manager_id else Employee.objects.all()
 
     if request.method == 'POST':
@@ -276,4 +282,5 @@
     })
 
+
 def add_tracks_to_playlist(request):
     playlists = Playlist.objects.all()
@@ -303,2 +310,38 @@
         'selected_playlist_id': selected_playlist_id
     })
+
+
+def add_invoice_lines_to_invoice(request):
+    invoices = Invoice.objects.all()
+    tracks = Track.objects.all()
+    selected_invoice_id = request.POST.get('invoice_id') or request.GET.get('invoice_id')
+
+    if request.method == 'POST':
+        selected_track_ids = request.POST.getlist('track_ids')
+        quantities = request.POST.getlist('quantities')
+
+        if selected_invoice_id and selected_track_ids and quantities:
+            try:
+                invoice_lines = []
+                for i in range(len(selected_track_ids)):
+                    track_id = int(selected_track_ids[i])
+                    quantity = int(quantities[i])
+                    invoice_lines.append({'track_id': track_id, 'quantity': quantity})
+
+                json_data = json.dumps(invoice_lines)
+
+                with connection.cursor() as cursor:
+                    cursor.execute("SELECT add_invoice_lines_to_existing_invoice(%s, %s::json);",
+                                   [selected_invoice_id, json_data])
+
+                messages.success(request, "Invoice lines added successfully.")
+                return redirect('add_invoice_lines_to_invoice')
+
+            except Exception as e:
+                messages.error(request, f"Error adding invoice lines: {e}")
+
+    return render(request, 'add_invoice_lines_to_invoice.html', {
+        'invoices': invoices,
+        'tracks': tracks,
+        'selected_invoice_id': selected_invoice_id
+    })
Index: templates/add_invoice_lines_to_invoice.html
===================================================================
--- templates/add_invoice_lines_to_invoice.html	(revision d4c80c07957ce76ec98052794bc5a3da8d5f08d0)
+++ templates/add_invoice_lines_to_invoice.html	(revision d4c80c07957ce76ec98052794bc5a3da8d5f08d0)
@@ -0,0 +1,64 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.5/dist/css/bootstrap.min.css" rel="stylesheet"
+          integrity="sha384-SgOJa3DmI69IUzQ2PVdRZhwQ+dy64/BUtbMJw1MZ8t5HZApcHrRKUc4W0kG879m7" crossorigin="anonymous">
+    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.5/dist/js/bootstrap.bundle.min.js"
+            integrity="sha384-k6d4wzSIapyDyv1kpU366/PK5hCdSbCRGRCMv+eplOQJWyd1fbcAu9OCUj5zNLiq"
+            crossorigin="anonymous"></script>
+    <title>Track Count Per Genre</title>
+</head>
+<body class="d-flex bg-light">
+{% include 'sidebar.html' %}
+<div class="container mt-5">
+    <h1 class="text-center mb-4">Add Invoice Lines</h1>
+
+    <form method="post" class="card p-4 shadow-sm bg-white">
+        {% csrf_token %}
+
+        <div class="mb-3">
+            <label for="invoice_id" class="form-label"><strong>Select Invoice</strong></label>
+            <select name="invoice_id" id="invoice_id" class="form-select" onchange="this.form.submit()">
+                <option value="">-- Choose Invoice --</option>
+                {% for invoice in invoices %}
+                    <option value="{{ invoice.invoice_id }}"
+                            {% if invoice.invoice_id|stringformat:"s" == selected_invoice_id %}selected{% endif %}>
+                        Invoice #{{ invoice.invoice_id }} - {{ invoice.invoice_date }}
+                    </option>
+                {% endfor %}
+            </select>
+        </div>
+
+        <div class="row">
+            <div class="col-6">
+
+
+                <div class="mb-3">
+                    <label class="form-label"><strong>Select Tracks and Quantities</strong></label>
+                    {% for track in tracks %}
+                        <div class="row mb-2">
+                            <div class="col-auto">
+                                <input class="form-check-input" type="checkbox" name="track_ids"
+                                       value="{{ track.track_id }}" id="track{{ track.track_id }}">
+                                <label class="form-check-label" for="track{{ track.track_id }}">
+                                    {{ track.name }}
+                                </label>
+                            </div>
+                            <div class="col">
+                                <input type="number" class="form-control" name="quantities" min="1" value="1"
+                                       placeholder="Quantity">
+                            </div>
+                        </div>
+                    {% endfor %}
+                </div>
+            </div>
+            <div class="col-4 mx-auto">
+                <button type="submit" class="btn btn-primary px-5">Add to Invoice</button>
+            </div>
+
+        </div>
+
+    </form>
+</div>
+</body>
+</html>
Index: templates/sidebar.html
===================================================================
--- templates/sidebar.html	(revision d0b1ea74bdcbf92413abee6cdf506065f9e4a08e)
+++ templates/sidebar.html	(revision d4c80c07957ce76ec98052794bc5a3da8d5f08d0)
@@ -82,5 +82,5 @@
         <li class="nav-item">
             <a href="{% url 'batch_update_reports_to' %}"
-               class="nav-link {% if request.path == 'employee/batch-update-reports-to/' %}active{% endif %}">
+               class="nav-link {% if request.path == '/employee/batch-update-reports-to/' %}active{% endif %}">
                 Update manager
             </a>
@@ -88,8 +88,15 @@
        <li class="nav-item">
             <a href="{% url 'add_tracks_to_playlist' %}"
-               class="nav-link {% if request.path == 'playlists/add-tracks/' %}active{% endif %}">
+               class="nav-link {% if request.path == '/playlists/add-tracks/' %}active{% endif %}">
                 Add tracks to playlist
             </a>
         </li>
+         <li class="nav-item">
+            <a href="{% url 'add_invoice_lines_to_invoice' %}"
+               class="nav-link {% if request.path == '/invoices/add-lines/' %}active{% endif %}">
+                Add invoice lines
+            </a>
+        </li>
     </ul>
+
 </div>