diff --git a/client/src/components/admin/KreditorTable.js b/client/src/components/admin/KreditorTable.js
index 0968922..5c309c7 100644
--- a/client/src/components/admin/KreditorTable.js
+++ b/client/src/components/admin/KreditorTable.js
@@ -196,7 +196,7 @@ class KreditorTable extends Component {
     }, 100);
 
     try {
-      const response = await this.authService.apiCall(`/admin/kreditoren/${kreditor.id}`, {
+      const response = await this.authService.apiCall(`/admin/kreditoren/${itemToDelete.id}`, {
         method: 'DELETE',
       });
 
diff --git a/client/src/components/cellRenderers/DocumentRenderer.js b/client/src/components/cellRenderers/DocumentRenderer.js
index 157e642..befebf3 100644
--- a/client/src/components/cellRenderers/DocumentRenderer.js
+++ b/client/src/components/cellRenderers/DocumentRenderer.js
@@ -350,7 +350,15 @@ const DocumentRenderer = (params) => {
         aria-describedby="document-dialog-content"
       >
         <DialogTitle id="document-dialog-title">
-          {hasDocuments ? `Dokumente (${totalCount})` : 'Dokumentinformationen'}
+          {(() => {
+            const beschreibung = params?.data?.description || '';
+            const beschreibungTrimmed = beschreibung ? String(beschreibung).slice(0, 120) : '';
+            if (hasDocuments) {
+              return `Dokumente (${totalCount})${beschreibungTrimmed ? ' — ' + beschreibungTrimmed : ''}`;
+            }
+            // No documents: still include description next to "Dokumentinformationen"
+            return `Dokumentinformationen${beschreibungTrimmed ? ' — ' + beschreibungTrimmed : ''}`;
+          })()}
         </DialogTitle>
         <DialogContent sx={{ p: 0 }} id="document-dialog-content">
           {error && (
@@ -367,13 +375,13 @@ const DocumentRenderer = (params) => {
                 sx={{
                   color: !params.data['Kontonummer/IBAN'] 
                     ? 'text.secondary' 
-                    : params.data.hasKreditor 
+                    : (params.data.hasKreditor && params.data.kreditor && !params.data.kreditor.is_banking)
                       ? 'success.main' 
                       : 'warning.main',
                   '&.Mui-selected': {
                     color: !params.data['Kontonummer/IBAN'] 
                       ? 'text.secondary' 
-                      : params.data.hasKreditor 
+                      : (params.data.hasKreditor && params.data.kreditor && !params.data.kreditor.is_banking)
                         ? 'success.main' 
                         : 'warning.main',
                   }
diff --git a/client/src/services/KreditorService.js b/client/src/services/KreditorService.js
index a8ba4e6..59baa6c 100644
--- a/client/src/services/KreditorService.js
+++ b/client/src/services/KreditorService.js
@@ -1,5 +1,6 @@
 class KreditorService {
   constructor() {
+    // API is mounted under /api (see src/index.js). Keep consistent with AuthService.
     this.baseURL = '/api';
   }
 
@@ -45,7 +46,8 @@ class KreditorService {
 
   async getAllKreditors() {
     try {
-      const response = await fetch(`${this.baseURL}/data/kreditors`, {
+      const url = `${this.baseURL}/data/kreditors`;
+      const response = await fetch(url, {
         method: 'GET',
         headers: await this.getAuthHeaders(),
       });
@@ -53,19 +55,23 @@ class KreditorService {
       return await this.handleResponse(response);
     } catch (error) {
       console.error('Error fetching kreditors:', error);
-      
-      // Handle network errors
       if (error instanceof TypeError && error.message.includes('fetch')) {
         throw new Error('FibDash Service nicht erreichbar - Prüfen Sie Ihre Internetverbindung oder versuchen Sie es später erneut');
       }
-      
       throw error;
     }
   }
 
+  // Convenience: find kreditor by kreditorId (string compare)
+  async findKreditorByCode(kreditorId) {
+    const all = await this.getAllKreditors();
+    return (all || []).find(k => String(k.kreditorId).trim() === String(kreditorId).trim());
+  }
+
   async getKreditorById(id) {
     try {
-      const response = await fetch(`${this.baseURL}/data/kreditors/${id}`, {
+      const url = `${this.baseURL}/data/kreditors/${id}`;
+      const response = await fetch(url, {
         method: 'GET',
         headers: await this.getAuthHeaders(),
       });
@@ -73,19 +79,18 @@ class KreditorService {
       return await this.handleResponse(response);
     } catch (error) {
       console.error('Error fetching kreditor:', error);
-      
-      // Handle network errors
       if (error instanceof TypeError && error.message.includes('fetch')) {
         throw new Error('FibDash Service nicht erreichbar - Prüfen Sie Ihre Internetverbindung oder versuchen Sie es später erneut');
       }
-      
       throw error;
     }
   }
 
   async createKreditor(kreditorData) {
     try {
-      const response = await fetch(`${this.baseURL}/data/kreditors`, {
+      const url = `${this.baseURL}/data/kreditors`;
+      console.debug('[KreditorService] POST', url, kreditorData);
+      const response = await fetch(url, {
         method: 'POST',
         headers: await this.getAuthHeaders(),
         body: JSON.stringify(kreditorData),
@@ -93,20 +98,23 @@ class KreditorService {
 
       return await this.handleResponse(response);
     } catch (error) {
+      // Map unique constraint errors to a clearer duplicate message when possible
+      const msg = (error && error.message) || '';
+      if (/unique|bereits vorhanden|already exists|kreditor/i.test(msg)) {
+        throw new Error('Kreditor bereits vorhanden');
+      }
       console.error('Error creating kreditor:', error);
-      
-      // Handle network errors
       if (error instanceof TypeError && error.message.includes('fetch')) {
         throw new Error('FibDash Service nicht erreichbar - Prüfen Sie Ihre Internetverbindung oder versuchen Sie es später erneut');
       }
-      
       throw error;
     }
   }
 
   async updateKreditor(id, kreditorData) {
     try {
-      const response = await fetch(`${this.baseURL}/data/kreditors/${id}`, {
+      const url = `${this.baseURL}/data/kreditors/${id}`;
+      const response = await fetch(url, {
         method: 'PUT',
         headers: await this.getAuthHeaders(),
         body: JSON.stringify(kreditorData),
@@ -115,19 +123,17 @@ class KreditorService {
       return await this.handleResponse(response);
     } catch (error) {
       console.error('Error updating kreditor:', error);
-      
-      // Handle network errors
       if (error instanceof TypeError && error.message.includes('fetch')) {
         throw new Error('FibDash Service nicht erreichbar - Prüfen Sie Ihre Internetverbindung oder versuchen Sie es später erneut');
       }
-      
       throw error;
     }
   }
 
   async deleteKreditor(id) {
     try {
-      const response = await fetch(`${this.baseURL}/data/kreditors/${id}`, {
+      const url = `${this.baseURL}/data/kreditors/${id}`;
+      const response = await fetch(url, {
         method: 'DELETE',
         headers: await this.getAuthHeaders(),
       });
@@ -135,12 +141,9 @@ class KreditorService {
       return await this.handleResponse(response);
     } catch (error) {
       console.error('Error deleting kreditor:', error);
-      
-      // Handle network errors
       if (error instanceof TypeError && error.message.includes('fetch')) {
         throw new Error('FibDash Service nicht erreichbar - Prüfen Sie Ihre Internetverbindung oder versuchen Sie es später erneut');
       }
-      
       throw error;
     }
   }
diff --git a/src/routes/admin.js b/src/routes/admin.js
index fe0d0fe..1a93a11 100644
--- a/src/routes/admin.js
+++ b/src/routes/admin.js
@@ -270,4 +270,4 @@ router.delete('/buchungsschluessel/:id', authenticateToken, async (req, res) =>
   }
 });
 
-module.exports = router; 
\ No newline at end of file
+module.exports = router; 
diff --git a/src/routes/data/bankingTransactions.js b/src/routes/data/bankingTransactions.js
index 20460b8..6344277 100644
--- a/src/routes/data/bankingTransactions.js
+++ b/src/routes/data/bankingTransactions.js
@@ -143,8 +143,8 @@ router.get('/assignable-kreditors', authenticateToken, async (req, res) => {
     
     const query = `
       SELECT id, name, kreditorId
-      FROM fibdash.Kreditor 
-      WHERE is_banking = 0
+      FROM fibdash.Kreditor
+      WHERE (is_banking = 0 OR is_banking IS NULL)
       ORDER BY name
     `;
     
diff --git a/src/routes/data/kreditors.js b/src/routes/data/kreditors.js
index 91398ef..0adb5df 100644
--- a/src/routes/data/kreditors.js
+++ b/src/routes/data/kreditors.js
@@ -58,8 +58,9 @@ router.post('/kreditors', authenticateToken, async (req, res) => {
       return res.status(400).json({ error: 'Name and kreditorId are required' });
     }
     
-    if (!isBanking && (!iban || iban.trim() === '')) {
-      return res.status(400).json({ error: 'IBAN is required (except for banking accounts)' });
+    // Business rule: IBAN is required for banking kreditors (proxies), not required for real kreditors
+    if (isBanking && (!iban || iban.trim() === '')) {
+      return res.status(400).json({ error: 'IBAN is required for banking kreditors' });
     }
     
     if (iban && iban.trim() !== '') {
@@ -108,8 +109,9 @@ router.put('/kreditors/:id', authenticateToken, async (req, res) => {
       return res.status(400).json({ error: 'Name and kreditorId are required' });
     }
     
-    if (!isBanking && (!iban || iban.trim() === '')) {
-      return res.status(400).json({ error: 'IBAN is required (except for banking accounts)' });
+    // Business rule: IBAN is required for banking kreditors (proxies), not required for real kreditors
+    if (isBanking && (!iban || iban.trim() === '')) {
+      return res.status(400).json({ error: 'IBAN is required for banking kreditors' });
     }
     
     const checkQuery = `SELECT id FROM fibdash.Kreditor WHERE id = @id`;