diff --git a/public/app.js b/public/app.js
index 4bac4e7..6e9c643 100644
--- a/public/app.js
+++ b/public/app.js
@@ -817,7 +817,7 @@ async function openInvoiceModal(invoiceId = null) {
             }
         }
         
-        document.getElementById('invoice-number').value = data.invoice.invoice_number;
+        document.getElementById('invoice-number').value = data.invoice.invoice_number || '';
         document.getElementById('invoice-customer').value = data.invoice.customer_id;
         const dateOnly = data.invoice.invoice_date.split('T')[0];
         document.getElementById('invoice-date').value = dateOnly;
@@ -825,6 +825,14 @@ async function openInvoiceModal(invoiceId = null) {
         document.getElementById('invoice-authorization').value = data.invoice.auth_code || '';
         document.getElementById('invoice-tax-exempt').checked = data.invoice.tax_exempt;
         
+        // Scheduled Send Date
+        const sendDateEl = document.getElementById('invoice-send-date');
+        if (sendDateEl) {
+            sendDateEl.value = data.invoice.scheduled_send_date 
+                ? data.invoice.scheduled_send_date.split('T')[0] 
+                : '';
+        }
+        
         // Load items
         document.getElementById('invoice-items').innerHTML = '';
         itemCounter = 0;
@@ -838,11 +846,12 @@ async function openInvoiceModal(invoiceId = null) {
         document.getElementById('invoice-form').reset();
         document.getElementById('invoice-items').innerHTML = '';
         document.getElementById('invoice-terms').value = 'Net 30';
+        document.getElementById('invoice-number').value = '';  // Leer lassen!
+        document.getElementById('invoice-send-date').value = '';
         itemCounter = 0;
         setDefaultDate();
         
-        // Fetch next invoice number
-        fetchNextInvoiceNumber();
+        // KEIN fetchNextInvoiceNumber() mehr — Nummer kommt von QBO
         
         // Add one default item
         addInvoiceItem();
@@ -1068,39 +1077,49 @@ async function handleInvoiceSubmit(e) {
         return;
     }
     
-    const invoiceNumber = document.getElementById('invoice-number').value;
+    const invoiceNumber = document.getElementById('invoice-number').value.trim();
     
-    if (!invoiceNumber || !/^\d+$/.test(invoiceNumber)) {
-        alert('Invalid invoice number. Must be a numeric value.');
+    // Invoice Number ist jetzt OPTIONAL
+    // Wenn angegeben, muss sie numerisch sein
+    if (invoiceNumber && !/^\d+$/.test(invoiceNumber)) {
+        alert('Invalid invoice number. Must be a numeric value or left empty.');
         return;
     }
     
     const data = {
-        invoice_number: invoiceNumber,
+        invoice_number: invoiceNumber || null,  // null wenn leer
         customer_id: parseInt(document.getElementById('invoice-customer').value),
         invoice_date: document.getElementById('invoice-date').value,
         terms: document.getElementById('invoice-terms').value,
         auth_code: document.getElementById('invoice-authorization').value,
         tax_exempt: document.getElementById('invoice-tax-exempt').checked,
+        scheduled_send_date: document.getElementById('invoice-send-date').value || null,
         items: items
     };
     
     try {
-        const url = currentInvoiceId ? `/api/invoices/${currentInvoiceId}` : '/api/invoices';
-        const method = currentInvoiceId ? 'PUT' : 'POST';
+        let response;
+        if (currentInvoiceId) {
+            response = await fetch(`/api/invoices/${currentInvoiceId}`, {
+                method: 'PUT',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify(data)
+            });
+        } else {
+            response = await fetch('/api/invoices', {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify(data)
+            });
+        }
         
-        const response = await fetch(url, {
-            method,
-            headers: { 'Content-Type': 'application/json' },
-            body: JSON.stringify(data)
-        });
+        const result = await response.json();
         
         if (response.ok) {
             closeInvoiceModal();
             loadInvoices();
         } else {
-            const error = await response.json();
-            alert(error.error || 'Error saving invoice');
+            alert(result.error || 'Error saving invoice');
         }
     } catch (error) {
         console.error('Error:', error);
diff --git a/public/index.html b/public/index.html
index d13275b..c693081 100644
--- a/public/index.html
+++ b/public/index.html
@@ -65,7 +65,7 @@
                 </div>
             </div>
 
-            <!-- Invoices Tab -->
+           <!-- Invoices Tab -->
             <div id="invoices-tab" class="tab-content hidden">
                 <div class="flex justify-between items-center mb-4">
                     <h2 class="text-3xl font-bold text-gray-800">Invoices</h2>
@@ -81,12 +81,13 @@
                     <table class="min-w-full divide-y divide-gray-200">
                         <thead class="bg-gray-50">
                             <tr>
-                                <th class="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Invoice #</th>
-                                <th class="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Customer</th>
-                                <th class="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Date</th>
-                                <th class="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Terms</th>
-                                <th class="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Total</th>
-                                <th class="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Actions</th>
+                                <th class="px-4 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Invoice #</th>
+                                <th class="px-4 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Customer</th>
+                                <th class="px-4 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Date</th>
+                                <th class="px-4 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Send Date</th>
+                                <th class="px-4 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Terms</th>
+                                <th class="px-4 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Total</th>
+                                <th class="px-4 py-3 text-left text-xs font-medium text-gray-500 uppercase tracking-wider">Actions</th>
                             </tr>
                         </thead>
                         <tbody id="invoices-list" class="bg-white divide-y divide-gray-200">
@@ -444,12 +445,13 @@
             </div>
             
             <form id="invoice-form" class="space-y-6">
-                <div class="grid grid-cols-5 gap-4">
+               <div class="grid grid-cols-6 gap-4">
                     <div>
                         <label class="block text-sm font-medium text-gray-700 mb-1">Invoice #</label>
-                        <input type="text" id="invoice-number" required pattern="[0-9]+" 
-                               class="w-full px-4 py-2 border border-gray-300 rounded-md focus:ring-blue-500 focus:border-blue-500"
-                               title="Must be a numeric value">
+                        <input type="text" id="invoice-number" pattern="[0-9]*" 
+                               placeholder="Auto (QBO)"
+                               class="w-full px-4 py-2 border border-gray-300 rounded-md focus:ring-blue-500 focus:border-blue-500 bg-gray-50"
+                               title="Optional — wird beim QBO Export automatisch vergeben">
                     </div>
                     <div x-data="customerSearch('invoice')" class="relative">
                         <label class="block text-sm font-medium text-gray-700 mb-1">Customer</label>
@@ -492,6 +494,12 @@
                         <input type="date" id="invoice-date" required 
                                class="w-full px-4 py-2 border border-gray-300 rounded-md focus:ring-blue-500 focus:border-blue-500">
                     </div>
+                    <div>
+                        <label class="block text-sm font-medium text-gray-700 mb-1">Send Date</label>
+                        <input type="date" id="invoice-send-date" 
+                               class="w-full px-4 py-2 border border-gray-300 rounded-md focus:ring-blue-500 focus:border-blue-500"
+                               title="Wann soll die Rechnung versendet werden?">
+                    </div>
                     <div>
                         <label class="block text-sm font-medium text-gray-700 mb-1">Terms</label>
                         <input type="text" id="invoice-terms" value="Net 30" required 
diff --git a/public/invoice-view.js b/public/invoice-view.js
index 612dadc..854794b 100644
--- a/public/invoice-view.js
+++ b/public/invoice-view.js
@@ -1,6 +1,5 @@
 // invoice-view.js — ES Module für die Invoice View
-// Features: Status Filter (all/unpaid/paid/overdue), Customer Filter,
-// Group by (none/week/month), Sortierung neueste zuerst, Mark Paid/Unpaid
+// Features: Status Filter, Customer Filter, Group by, Send Date, Mark Paid, Reset QBO
 
 // ============================================================
 // State
@@ -17,6 +16,7 @@ const OVERDUE_DAYS = 30;
 // ============================================================
 
 function formatDate(date) {
+    if (!date) return '—';
     const d = new Date(date);
     const month = String(d.getMonth() + 1).padStart(2, '0');
     const day = String(d.getDate()).padStart(2, '0');
@@ -97,7 +97,6 @@ function getFilteredInvoices() {
     } else if (filterStatus === 'overdue') {
         filtered = filtered.filter(inv => isOverdue(inv));
     }
-    // 'all' → kein Filter
 
     // Customer Filter
     if (filterCustomer.trim()) {
@@ -142,12 +141,10 @@ function groupInvoices(filtered) {
         group.total += parseFloat(inv.total) || 0;
     });
 
-    // Innerhalb jeder Gruppe nochmal nach Datum sortieren (neueste zuerst)
     for (const group of groups.values()) {
         group.invoices.sort((a, b) => new Date(b.invoice_date) - new Date(a.invoice_date));
     }
 
-    // Gruppen nach Key sortieren (neueste zuerst)
     return new Map([...groups.entries()].sort((a, b) => b[0].localeCompare(a[0])));
 }
 
@@ -160,12 +157,17 @@ function renderInvoiceRow(invoice) {
     const paid = isPaid(invoice);
     const overdue = isOverdue(invoice);
 
-    // QBO Button
+    // Invoice Number Display
+    const invNumDisplay = invoice.invoice_number 
+        ? invoice.invoice_number 
+        : `<span class="text-gray-400 italic text-xs">Draft</span>`;
+
+    // QBO Button — if already in QBO, show checkmark + optional reset
     const qboButton = hasQbo
-        ? `<span class="text-gray-400 text-xs" title="Already in QBO (ID: ${invoice.qbo_id})">✓ QBO</span>`
+        ? `<span class="text-gray-400 text-xs cursor-pointer" title="In QBO (ID: ${invoice.qbo_id}) — Click to reset" onclick="window.invoiceView.resetQbo(${invoice.id})">✓ QBO</span>`
         : `<button onclick="window.invoiceView.exportToQBO(${invoice.id})" class="text-orange-600 hover:text-orange-900" title="Export to QuickBooks">QBO Export</button>`;
 
-    // Paid/Unpaid Toggle Button
+    // Paid/Unpaid Toggle
     const paidButton = paid
         ? `<button onclick="window.invoiceView.markUnpaid(${invoice.id})" class="text-yellow-600 hover:text-yellow-800" title="Mark as unpaid">↩ Unpaid</button>`
         : `<button onclick="window.invoiceView.markPaid(${invoice.id})" class="text-emerald-600 hover:text-emerald-800" title="Mark as paid">💰 Paid</button>`;
@@ -175,28 +177,50 @@ function renderInvoiceRow(invoice) {
     if (paid) {
         statusBadge = `<span class="inline-block px-2 py-0.5 text-xs font-semibold rounded-full bg-green-100 text-green-800" title="Paid ${formatDate(invoice.paid_date)}">Paid</span>`;
     } else if (overdue) {
-        statusBadge = `<span class="inline-block px-2 py-0.5 text-xs font-semibold rounded-full bg-red-100 text-red-800" title="${daysSince(invoice.invoice_date)} days old">Overdue</span>`;
+        statusBadge = `<span class="inline-block px-2 py-0.5 text-xs font-semibold rounded-full bg-red-100 text-red-800" title="${daysSince(invoice.invoice_date)} days">Overdue</span>`;
+    }
+
+    // Send Date display
+    let sendDateDisplay = '—';
+    if (invoice.scheduled_send_date) {
+        const sendDate = new Date(invoice.scheduled_send_date);
+        const today = new Date();
+        today.setHours(0,0,0,0);
+        sendDate.setHours(0,0,0,0);
+        
+        const daysUntil = Math.floor((sendDate - today) / 86400000);
+        sendDateDisplay = formatDate(invoice.scheduled_send_date);
+        
+        if (!paid) {
+            if (daysUntil < 0) {
+                sendDateDisplay += ` <span class="text-xs text-red-500">(${Math.abs(daysUntil)}d ago)</span>`;
+            } else if (daysUntil === 0) {
+                sendDateDisplay += ` <span class="text-xs text-orange-500 font-semibold">(today)</span>`;
+            } else if (daysUntil <= 3) {
+                sendDateDisplay += ` <span class="text-xs text-yellow-600">(in ${daysUntil}d)</span>`;
+            }
+        }
     }
 
-    // Row styling
     const rowClass = paid ? 'bg-green-50/50' : overdue ? 'bg-red-50/50' : '';
 
     return `
         <tr class="${rowClass}">
-            <td class="px-6 py-4 whitespace-nowrap text-sm font-medium text-gray-900">
-                ${invoice.invoice_number} ${statusBadge}
+            <td class="px-4 py-3 whitespace-nowrap text-sm font-medium text-gray-900">
+                ${invNumDisplay} ${statusBadge}
             </td>
-            <td class="px-6 py-4 text-sm text-gray-500">${invoice.customer_name || 'N/A'}</td>
-            <td class="px-6 py-4 whitespace-nowrap text-sm text-gray-500">${formatDate(invoice.invoice_date)}</td>
-            <td class="px-6 py-4 whitespace-nowrap text-sm text-gray-500">${invoice.terms}</td>
-            <td class="px-6 py-4 whitespace-nowrap text-sm text-gray-900 font-semibold">$${parseFloat(invoice.total).toFixed(2)}</td>
-            <td class="px-6 py-4 whitespace-nowrap text-sm font-medium space-x-2">
+            <td class="px-4 py-3 text-sm text-gray-500">${invoice.customer_name || 'N/A'}</td>
+            <td class="px-4 py-3 whitespace-nowrap text-sm text-gray-500">${formatDate(invoice.invoice_date)}</td>
+            <td class="px-4 py-3 whitespace-nowrap text-sm text-gray-500">${sendDateDisplay}</td>
+            <td class="px-4 py-3 whitespace-nowrap text-sm text-gray-500">${invoice.terms}</td>
+            <td class="px-4 py-3 whitespace-nowrap text-sm text-gray-900 font-semibold">$${parseFloat(invoice.total).toFixed(2)}</td>
+            <td class="px-4 py-3 whitespace-nowrap text-sm font-medium space-x-1">
                 <button onclick="window.invoiceView.viewPDF(${invoice.id})" class="text-green-600 hover:text-green-900">PDF</button>
                 <button onclick="window.invoiceView.viewHTML(${invoice.id})" class="text-teal-600 hover:text-teal-900">HTML</button>
                 ${qboButton}
                 ${paidButton}
                 <button onclick="window.invoiceView.edit(${invoice.id})" class="text-blue-600 hover:text-blue-900">Edit</button>
-                <button onclick="window.invoiceView.remove(${invoice.id})" class="text-red-600 hover:text-red-900">Delete</button>
+                <button onclick="window.invoiceView.remove(${invoice.id})" class="text-red-600 hover:text-red-900">Del</button>
             </td>
         </tr>
     `;
@@ -205,7 +229,7 @@ function renderInvoiceRow(invoice) {
 function renderGroupHeader(label) {
     return `
         <tr class="bg-blue-50">
-            <td colspan="6" class="px-6 py-3 text-sm font-bold text-blue-800">
+            <td colspan="7" class="px-4 py-3 text-sm font-bold text-blue-800">
                 📅 ${label}
             </td>
         </tr>
@@ -215,8 +239,8 @@ function renderGroupHeader(label) {
 function renderGroupFooter(total, count) {
     return `
         <tr class="bg-gray-50 border-t-2 border-gray-300">
-            <td colspan="4" class="px-6 py-3 text-sm font-bold text-gray-700 text-right">Group Total (${count} invoices):</td>
-            <td class="px-6 py-3 text-sm font-bold text-gray-900">$${total.toFixed(2)}</td>
+            <td colspan="5" class="px-4 py-3 text-sm font-bold text-gray-700 text-right">Group Total (${count} invoices):</td>
+            <td class="px-4 py-3 text-sm font-bold text-gray-900">$${total.toFixed(2)}</td>
             <td></td>
         </tr>
     `;
@@ -245,8 +269,8 @@ export function renderInvoiceView() {
         if (groups.size > 1) {
             html += `
                 <tr class="bg-blue-100 border-t-4 border-blue-400">
-                    <td colspan="4" class="px-6 py-4 text-base font-bold text-blue-900 text-right">Grand Total (${filtered.length} invoices):</td>
-                    <td class="px-6 py-4 text-base font-bold text-blue-900">$${grandTotal.toFixed(2)}</td>
+                    <td colspan="5" class="px-4 py-4 text-base font-bold text-blue-900 text-right">Grand Total (${filtered.length} invoices):</td>
+                    <td class="px-4 py-4 text-base font-bold text-blue-900">$${grandTotal.toFixed(2)}</td>
                     <td></td>
                 </tr>
             `;
@@ -260,8 +284,8 @@ export function renderInvoiceView() {
         if (filtered.length > 0) {
             html += `
                 <tr class="bg-gray-100 border-t-2 border-gray-300">
-                    <td colspan="4" class="px-6 py-3 text-sm font-bold text-gray-700 text-right">Total (${filtered.length} invoices):</td>
-                    <td class="px-6 py-3 text-sm font-bold text-gray-900">$${grandTotal.toFixed(2)}</td>
+                    <td colspan="5" class="px-4 py-3 text-sm font-bold text-gray-700 text-right">Total (${filtered.length} invoices):</td>
+                    <td class="px-4 py-3 text-sm font-bold text-gray-900">$${grandTotal.toFixed(2)}</td>
                     <td></td>
                 </tr>
             `;
@@ -269,16 +293,14 @@ export function renderInvoiceView() {
     }
 
     if (filtered.length === 0) {
-        html = `<tr><td colspan="6" class="px-6 py-8 text-center text-gray-500">No invoices found.</td></tr>`;
+        html = `<tr><td colspan="7" class="px-6 py-8 text-center text-gray-500">No invoices found.</td></tr>`;
     }
 
     tbody.innerHTML = html;
 
-    // Update count badge
     const countEl = document.getElementById('invoice-count');
     if (countEl) countEl.textContent = filtered.length;
 
-    // Update status button active states
     updateStatusButtons();
 }
 
@@ -294,7 +316,6 @@ function updateStatusButtons() {
         }
     });
 
-    // Update overdue count badge
     const overdueCount = invoices.filter(inv => isOverdue(inv)).length;
     const overdueBadge = document.getElementById('overdue-badge');
     if (overdueBadge) {
@@ -306,7 +327,6 @@ function updateStatusButtons() {
         }
     }
 
-    // Update unpaid count
     const unpaidCount = invoices.filter(inv => !isPaid(inv)).length;
     const unpaidBadge = document.getElementById('unpaid-badge');
     if (unpaidBadge) {
@@ -315,7 +335,7 @@ function updateStatusButtons() {
 }
 
 // ============================================================
-// Toolbar HTML
+// Toolbar
 // ============================================================
 
 export function injectToolbar() {
@@ -377,7 +397,6 @@ export function injectToolbar() {
         </div>
     `;
 
-    // Event Listeners
     document.getElementById('invoice-filter-customer').addEventListener('input', (e) => {
         filterCustomer = e.target.value;
         renderInvoiceView();
@@ -433,6 +452,22 @@ export async function exportToQBO(id) {
     }
 }
 
+export async function resetQbo(id) {
+    if (!confirm('QBO-Verknüpfung zurücksetzen?\nDie Rechnung muss zuerst in QBO gelöscht werden!')) return;
+    
+    try {
+        const response = await fetch(`/api/invoices/${id}/reset-qbo`, { method: 'PATCH' });
+        if (response.ok) {
+            loadInvoices();
+        } else {
+            const err = await response.json();
+            alert('Error: ' + (err.error || 'Unknown'));
+        }
+    } catch (error) {
+        console.error('Error resetting QBO:', error);
+    }
+}
+
 export async function markPaid(id) {
     try {
         const response = await fetch(`/api/invoices/${id}/mark-paid`, {
@@ -493,6 +528,7 @@ window.invoiceView = {
     viewPDF,
     viewHTML,
     exportToQBO,
+    resetQbo,
     markPaid,
     markUnpaid,
     edit,
diff --git a/server.js b/server.js
index 8818e1e..2e1dff5 100644
--- a/server.js
+++ b/server.js
@@ -457,31 +457,32 @@ app.get('/api/invoices/:id', async (req, res) => {
 });
 
 app.post('/api/invoices', async (req, res) => {
-    const { invoice_number, customer_id, invoice_date, terms, auth_code, tax_exempt, items, created_from_quote_id } = req.body;
+    const { invoice_number, customer_id, invoice_date, terms, auth_code, tax_exempt, items, created_from_quote_id, scheduled_send_date } = req.body;
     
     const client = await pool.connect();
     try {
         await client.query('BEGIN');
         
-        // Validate invoice_number is provided and is numeric
-        if (!invoice_number || !/^\d+$/.test(invoice_number)) {
-            await client.query('ROLLBACK');
-            return res.status(400).json({ error: 'Invalid invoice number. Must be a numeric value.' });
-        }
-        
-        // Check if invoice number already exists
-        const existingInvoice = await client.query(
-            'SELECT id FROM invoices WHERE invoice_number = $1',
-            [invoice_number]
-        );
-        
-        if (existingInvoice.rows.length > 0) {
-            await client.query('ROLLBACK');
-            return res.status(400).json({ error: `Invoice number ${invoice_number} already exists.` });
+        // invoice_number ist jetzt OPTIONAL — wird erst beim QBO Export vergeben
+        // Wenn angegeben, muss sie numerisch sein und darf nicht existieren
+        if (invoice_number && invoice_number.trim() !== '') {
+            if (!/^\d+$/.test(invoice_number)) {
+                await client.query('ROLLBACK');
+                return res.status(400).json({ error: 'Invalid invoice number. Must be a numeric value.' });
+            }
+            
+            const existingInvoice = await client.query(
+                'SELECT id FROM invoices WHERE invoice_number = $1',
+                [invoice_number]
+            );
+            
+            if (existingInvoice.rows.length > 0) {
+                await client.query('ROLLBACK');
+                return res.status(400).json({ error: `Invoice number ${invoice_number} already exists.` });
+            }
         }
         
         let subtotal = 0;
-        
         for (const item of items) {
             const amount = parseFloat(item.amount.replace(/[$,]/g, ''));
             if (!isNaN(amount)) {
@@ -493,19 +494,22 @@ app.post('/api/invoices', async (req, res) => {
         const tax_amount = tax_exempt ? 0 : (subtotal * tax_rate / 100);
         const total = subtotal + tax_amount;
         
+        // invoice_number kann NULL sein
+        const invNum = (invoice_number && invoice_number.trim() !== '') ? invoice_number : null;
+        const sendDate = scheduled_send_date || null;
+        
         const invoiceResult = await client.query(
-            `INSERT INTO invoices (invoice_number, customer_id, invoice_date, terms, auth_code, tax_exempt, tax_rate, subtotal, tax_amount, total, created_from_quote_id)
-             VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11) RETURNING *`,
-            [invoice_number, customer_id, invoice_date, terms, auth_code, tax_exempt, tax_rate, subtotal, tax_amount, total, created_from_quote_id]
+            `INSERT INTO invoices (invoice_number, customer_id, invoice_date, terms, auth_code, tax_exempt, tax_rate, subtotal, tax_amount, total, created_from_quote_id, scheduled_send_date)
+             VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12) RETURNING *`,
+            [invNum, customer_id, invoice_date, terms, auth_code, tax_exempt, tax_rate, subtotal, tax_amount, total, created_from_quote_id, sendDate]
         );
         
         const invoiceId = invoiceResult.rows[0].id;
         
         for (let i = 0; i < items.length; i++) {
             await client.query(
-                // qbo_item_id hinzugefügt
                 'INSERT INTO invoice_items (invoice_id, quantity, description, rate, amount, item_order, qbo_item_id) VALUES ($1, $2, $3, $4, $5, $6, $7)',
-                [invoiceId, items[i].quantity, items[i].description, items[i].rate, items[i].amount, i, items[i].qbo_item_id || '9'] // Default '9' (Parts)
+                [invoiceId, items[i].quantity, items[i].description, items[i].rate, items[i].amount, i, items[i].qbo_item_id || '9']
             );
         }
         
@@ -556,7 +560,7 @@ app.post('/api/quotes/:id/convert-to-invoice', async (req, res) => {
             return res.status(400).json({ error: 'Cannot convert quote with TBD items to invoice. Please update all TBD items first.' });
         }
         
-        const invoice_number = await getNextInvoiceNumber();
+        const invoice_number = null; 
         const invoiceDate = new Date().toISOString().split('T')[0];
         
         const invoiceResult = await client.query(
@@ -588,31 +592,32 @@ app.post('/api/quotes/:id/convert-to-invoice', async (req, res) => {
 
 app.put('/api/invoices/:id', async (req, res) => {
     const { id } = req.params;
-    const { invoice_number, customer_id, invoice_date, terms, auth_code, tax_exempt, items } = req.body;
+    const { invoice_number, customer_id, invoice_date, terms, auth_code, tax_exempt, items, scheduled_send_date } = req.body;
     
     const client = await pool.connect();
     try {
         await client.query('BEGIN');
         
-        // Validate invoice_number is provided and is numeric
-        if (!invoice_number || !/^\d+$/.test(invoice_number)) {
+        // invoice_number ist optional. Wenn angegeben und nicht leer, muss sie numerisch sein
+        const invNum = (invoice_number && invoice_number.trim() !== '') ? invoice_number : null;
+        
+        if (invNum && !/^\d+$/.test(invNum)) {
             await client.query('ROLLBACK');
             return res.status(400).json({ error: 'Invalid invoice number. Must be a numeric value.' });
         }
         
-        // Check if invoice number already exists (excluding current invoice)
-        const existingInvoice = await client.query(
-            'SELECT id FROM invoices WHERE invoice_number = $1 AND id != $2',
-            [invoice_number, id]
-        );
-        
-        if (existingInvoice.rows.length > 0) {
-            await client.query('ROLLBACK');
-            return res.status(400).json({ error: `Invoice number ${invoice_number} already exists.` });
+        if (invNum) {
+            const existingInvoice = await client.query(
+                'SELECT id FROM invoices WHERE invoice_number = $1 AND id != $2',
+                [invNum, id]
+            );
+            if (existingInvoice.rows.length > 0) {
+                await client.query('ROLLBACK');
+                return res.status(400).json({ error: `Invoice number ${invNum} already exists.` });
+            }
         }
         
         let subtotal = 0;
-        
         for (const item of items) {
             const amount = parseFloat(item.amount.replace(/[$,]/g, ''));
             if (!isNaN(amount)) {
@@ -623,12 +628,13 @@ app.put('/api/invoices/:id', async (req, res) => {
         const tax_rate = 8.25;
         const tax_amount = tax_exempt ? 0 : (subtotal * tax_rate / 100);
         const total = subtotal + tax_amount;
+        const sendDate = scheduled_send_date || null;
         
         await client.query(
             `UPDATE invoices SET invoice_number = $1, customer_id = $2, invoice_date = $3, terms = $4, auth_code = $5, tax_exempt = $6, 
-             tax_rate = $7, subtotal = $8, tax_amount = $9, total = $10, updated_at = CURRENT_TIMESTAMP
-             WHERE id = $11`,
-            [invoice_number, customer_id, invoice_date, terms, auth_code, tax_exempt, tax_rate, subtotal, tax_amount, total, id]
+             tax_rate = $7, subtotal = $8, tax_amount = $9, total = $10, scheduled_send_date = $11, updated_at = CURRENT_TIMESTAMP
+             WHERE id = $12`,
+            [invNum, customer_id, invoice_date, terms, auth_code, tax_exempt, tax_rate, subtotal, tax_amount, total, sendDate, id]
         );
         
         await client.query('DELETE FROM invoice_items WHERE invoice_id = $1', [id]);
@@ -651,6 +657,7 @@ app.put('/api/invoices/:id', async (req, res) => {
     }
 });
 
+
 app.delete('/api/invoices/:id', async (req, res) => {
     const { id } = req.params;
     const client = await pool.connect();
@@ -1580,7 +1587,29 @@ app.patch('/api/invoices/:id/mark-unpaid', async (req, res) => {
     }
 });
 
-
+app.patch('/api/invoices/:id/reset-qbo', async (req, res) => {
+    const { id } = req.params;
+    
+    try {
+        const result = await pool.query(
+            `UPDATE invoices 
+             SET qbo_id = NULL, qbo_sync_token = NULL, qbo_doc_number = NULL, invoice_number = NULL, 
+                 updated_at = CURRENT_TIMESTAMP 
+             WHERE id = $1 RETURNING *`,
+            [id]
+        );
+        
+        if (result.rows.length === 0) {
+            return res.status(404).json({ error: 'Invoice not found' });
+        }
+        
+        console.log(`🔄 Invoice ID ${id} QBO-Verknüpfung zurückgesetzt`);
+        res.json(result.rows[0]);
+    } catch (error) {
+        console.error('Error resetting QBO link:', error);
+        res.status(500).json({ error: 'Error resetting QBO link' });
+    }
+});