diff --git a/public/js/main.js b/public/js/main.js
index 06b0df5..61609a9 100644
--- a/public/js/main.js
+++ b/public/js/main.js
@@ -549,6 +549,14 @@ function updateTimer() {
     document.getElementById('timerStatus').textContent = `Läuft seit ${timerStartTimeString} - Pause (${remainingMinutes} Min)`;
   } else {
     elapsed = Math.floor((now - timerStartTime) / 1000) - timerPausedDuration;
+    
+    // Check if 10h net time reached - auto stop timer
+    const netHours = elapsed / 3600;
+    if (netHours >= 10) {
+      showNotification('🛑 Maximale Arbeitszeit (10h netto) erreicht. Timer wird automatisch gestoppt.', 'warning');
+      stopWork();
+      return;
+    }
   }
   
   document.getElementById('timerDisplay').textContent = formatDuration(elapsed);
@@ -1686,6 +1694,13 @@ async function handleFormSubmit(e) {
     return;
   }
   
+  // Validate max 10h net time
+  const netHours = calculateNetHours(startTime, endTime, pauseMinutes);
+  if (netHours > 10) {
+    showNotification('❌ Maximale Arbeitszeit überschritten! Netto-Arbeitszeit darf maximal 10,0h betragen.', 'error');
+    return;
+  }
+  
   if (currentEditingId) {
     // Update existing entry
     const success = await updateEntry(currentEditingId, date, startTime, endTime, pauseMinutes, location);
@@ -1705,6 +1720,35 @@ async function handleFormSubmit(e) {
   }
 }
 
+/**
+ * Calculate net hours from times and pause
+ */
+function calculateNetHours(startTime, endTime, pauseMinutes) {
+  const [startHour, startMin] = startTime.split(':').map(Number);
+  const [endHour, endMin] = endTime.split(':').map(Number);
+  
+  const startMinutes = startHour * 60 + startMin;
+  const endMinutes = endHour * 60 + endMin;
+  
+  let grossMinutes = endMinutes - startMinutes;
+  if (grossMinutes < 0) grossMinutes += 24 * 60; // Handle overnight
+  
+  const grossHours = grossMinutes / 60;
+  
+  // Calculate pause if not provided
+  let pause = pauseMinutes || 0;
+  if (pauseMinutes === null || pauseMinutes === undefined) {
+    if (grossHours >= 9) {
+      pause = 45;
+    } else if (grossHours >= 6) {
+      pause = 30;
+    }
+  }
+  
+  const netHours = grossHours - (pause / 60);
+  return netHours;
+}
+
 /**
  * Handle delete button click
  */
@@ -2872,6 +2916,15 @@ function handleCellClick(e) {
       pauseToSend = null; // Trigger auto-calculation on server
     }
     
+    // Validate max 10h net time
+    const netHours = calculateNetHours(values.startTime, values.endTime, pauseToSend);
+    if (netHours > 10) {
+      showNotification('❌ Maximale Arbeitszeit überschritten! Netto-Arbeitszeit darf maximal 10,0h betragen.', 'error');
+      cell.classList.remove('editing');
+      cell.innerHTML = originalContent;
+      return;
+    }
+    
     // Update via API
     const success = await updateEntry(
       entryId,