This workflow follows the Error Trigger → Google Sheets recipe pattern — see all workflows that pair these two integrations.
The workflow JSON
Copy or download the full n8n JSON below. Paste it into a new n8n workflow, add your credentials, activate. Full import guide →
{
"name": "Invoice Data Extraction",
"nodes": [
{
"parameters": {
"content": "## Invoice Data Extraction\n\n**Purpose:** Extracts structured data from invoice text/images using AI, validates totals, and routes high-value invoices for human approval.\n\n**Flow:**\n1. Receive invoice via Webhook (POST raw text or base64 image)\n2. OpenAI extracts all invoice fields\n3. Validate and cross-check totals\n4. High-value invoices (>$5,000) pause for human approval\n5. Approved invoices are logged to Google Sheets\n6. Slack alert sent for high-value items\n\n**Setup Required:**\n- Configure Webhook URL in your invoice intake system\n- OpenAI API key\n- Google Sheets credential + Sheet ID\n- Slack credential\n- Set approval webhook URL in Wait node",
"height": 380,
"width": 400,
"color": 5
},
"id": "sticky-intro",
"name": "Intro Note",
"type": "n8n-nodes-base.stickyNote",
"typeVersion": 1,
"position": [
-500,
-220
]
},
{
"parameters": {
"content": "### Human Approval Gate\nFor invoices over $5,000 the workflow pauses here. A Slack message with Approve/Reject buttons is sent to the finance team. The workflow resumes when:\n- The approver clicks a button\n- OR the 48-hour timeout expires (auto-rejected)\n\nApproval webhook URL must match the Wait node's resume URL.",
"height": 200,
"width": 340,
"color": 4
},
"id": "sticky-approval",
"name": "Approval Note",
"type": "n8n-nodes-base.stickyNote",
"typeVersion": 1,
"position": [
1060,
-220
]
},
{
"parameters": {
"content": "### Retry Logic\nThe OpenAI call has a 30s timeout. If it fails, the Error Trigger catches it and retries via a separate sub-workflow call, or sends an alert for manual processing.",
"height": 160,
"width": 300,
"color": 3
},
"id": "sticky-retry",
"name": "Retry Note",
"type": "n8n-nodes-base.stickyNote",
"typeVersion": 1,
"position": [
1700,
460
]
},
{
"parameters": {
"httpMethod": "POST",
"path": "invoice-extract",
"responseMode": "lastNode",
"options": {
"rawBody": false
}
},
"id": "webhook-trigger",
"name": "Receive Invoice",
"type": "n8n-nodes-base.webhook",
"typeVersion": 2,
"position": [
-160,
60
]
},
{
"parameters": {
"method": "POST",
"url": "https://api.openai.com/v1/chat/completions",
"authentication": "genericCredentialType",
"genericAuthType": "httpHeaderAuth",
"sendHeaders": true,
"headerParameters": {
"parameters": [
{
"name": "Content-Type",
"value": "application/json"
}
]
},
"sendBody": true,
"specifyBody": "json",
"jsonBody": "={\n \"model\": \"gpt-4o\",\n \"temperature\": 0.1,\n \"response_format\": { \"type\": \"json_object\" },\n \"messages\": [\n {\n \"role\": \"system\",\n \"content\": \"You are an expert invoice data extraction AI. Extract ALL fields from the provided invoice text and return a JSON object with these exact fields:\\n\\n- vendor_name (string): name of the vendor/supplier\\n- vendor_address (string): full vendor address\\n- vendor_email (string): vendor email if present\\n- invoice_number (string): invoice or bill number\\n- invoice_date (string): invoice date in ISO 8601 format (YYYY-MM-DD)\\n- due_date (string): payment due date in ISO 8601 format (YYYY-MM-DD)\\n- po_number (string): purchase order number if present\\n- currency (string): 3-letter currency code e.g. USD, EUR, GBP\\n- subtotal (number): subtotal before tax\\n- tax_amount (number): total tax\\n- discount_amount (number): total discounts applied\\n- total_amount (number): grand total\\n- amount_due (number): amount still owed\\n- payment_terms (string): e.g. Net 30, Due on receipt\\n- line_items (array): array of objects, each with: description (string), quantity (number), unit_price (number), total (number)\\n- needs_review (boolean): true if data is ambiguous, totals don't match, or fields are missing\\n- review_reason (string): explanation if needs_review is true\\n\\nIf a field is not present in the invoice, use null. For numeric fields use 0 if not found. Return ONLY valid JSON.\"\n },\n {\n \"role\": \"user\",\n \"content\": \"Extract all data from this invoice:\\n\\n{{ $json.body.invoice_text || $json.body.text || JSON.stringify($json.body) }}\"\n }\n ]\n}",
"options": {
"timeout": 30000,
"retry": {
"enabled": true,
"maxTries": 2,
"waitBetweenTries": 3000
}
}
},
"id": "openai-extract",
"name": "OpenAI: Extract Invoice Data",
"type": "n8n-nodes-base.httpRequest",
"typeVersion": 4.2,
"position": [
80,
60
],
"credentials": {
"httpHeaderAuth": {
"name": "<your credential>"
}
}
},
{
"parameters": {
"assignments": {
"assignments": [
{
"id": "v1",
"name": "vendor_name",
"value": "={{ JSON.parse($json.choices[0].message.content).vendor_name || 'Unknown Vendor' }}",
"type": "string"
},
{
"id": "v2",
"name": "vendor_address",
"value": "={{ JSON.parse($json.choices[0].message.content).vendor_address || '' }}",
"type": "string"
},
{
"id": "v3",
"name": "vendor_email",
"value": "={{ JSON.parse($json.choices[0].message.content).vendor_email || '' }}",
"type": "string"
},
{
"id": "v4",
"name": "invoice_number",
"value": "={{ JSON.parse($json.choices[0].message.content).invoice_number || 'N/A' }}",
"type": "string"
},
{
"id": "v5",
"name": "invoice_date",
"value": "={{ JSON.parse($json.choices[0].message.content).invoice_date || '' }}",
"type": "string"
},
{
"id": "v6",
"name": "due_date",
"value": "={{ JSON.parse($json.choices[0].message.content).due_date || '' }}",
"type": "string"
},
{
"id": "v7",
"name": "po_number",
"value": "={{ JSON.parse($json.choices[0].message.content).po_number || '' }}",
"type": "string"
},
{
"id": "v8",
"name": "currency",
"value": "={{ JSON.parse($json.choices[0].message.content).currency || 'USD' }}",
"type": "string"
},
{
"id": "v9",
"name": "subtotal",
"value": "={{ JSON.parse($json.choices[0].message.content).subtotal || 0 }}",
"type": "number"
},
{
"id": "v10",
"name": "tax_amount",
"value": "={{ JSON.parse($json.choices[0].message.content).tax_amount || 0 }}",
"type": "number"
},
{
"id": "v11",
"name": "discount_amount",
"value": "={{ JSON.parse($json.choices[0].message.content).discount_amount || 0 }}",
"type": "number"
},
{
"id": "v12",
"name": "total_amount",
"value": "={{ JSON.parse($json.choices[0].message.content).total_amount || 0 }}",
"type": "number"
},
{
"id": "v13",
"name": "amount_due",
"value": "={{ JSON.parse($json.choices[0].message.content).amount_due || JSON.parse($json.choices[0].message.content).total_amount || 0 }}",
"type": "number"
},
{
"id": "v14",
"name": "payment_terms",
"value": "={{ JSON.parse($json.choices[0].message.content).payment_terms || '' }}",
"type": "string"
},
{
"id": "v15",
"name": "line_items_json",
"value": "={{ JSON.stringify(JSON.parse($json.choices[0].message.content).line_items || []) }}",
"type": "string"
},
{
"id": "v16",
"name": "line_items_count",
"value": "={{ (JSON.parse($json.choices[0].message.content).line_items || []).length }}",
"type": "number"
},
{
"id": "v17",
"name": "needs_review",
"value": "={{ JSON.parse($json.choices[0].message.content).needs_review || false }}",
"type": "boolean"
},
{
"id": "v18",
"name": "review_reason",
"value": "={{ JSON.parse($json.choices[0].message.content).review_reason || '' }}",
"type": "string"
},
{
"id": "v19",
"name": "calculated_total",
"value": "={{ (JSON.parse($json.choices[0].message.content).subtotal || 0) + (JSON.parse($json.choices[0].message.content).tax_amount || 0) - (JSON.parse($json.choices[0].message.content).discount_amount || 0) }}",
"type": "number"
},
{
"id": "v20",
"name": "totals_match",
"value": "={{ Math.abs((JSON.parse($json.choices[0].message.content).subtotal || 0) + (JSON.parse($json.choices[0].message.content).tax_amount || 0) - (JSON.parse($json.choices[0].message.content).discount_amount || 0) - (JSON.parse($json.choices[0].message.content).total_amount || 0)) < 0.02 }}",
"type": "boolean"
},
{
"id": "v21",
"name": "extracted_at",
"value": "={{ new Date().toISOString() }}",
"type": "string"
},
{
"id": "v22",
"name": "submission_id",
"value": "={{ $json.choices[0].message.content ? 'INV-' + Date.now() : '' }}",
"type": "string"
}
]
},
"options": {}
},
"id": "set-validate",
"name": "Validate & Parse Totals",
"type": "n8n-nodes-base.set",
"typeVersion": 3.4,
"position": [
320,
60
]
},
{
"parameters": {
"conditions": {
"options": {
"caseSensitive": false,
"leftValue": "",
"typeValidation": "strict"
},
"conditions": [
{
"id": "c1",
"leftValue": "={{ $json.total_amount }}",
"rightValue": 5000,
"operator": {
"type": "number",
"operation": "gt"
}
}
],
"combinator": "and"
},
"options": {}
},
"id": "if-high-value",
"name": "Total > $5,000?",
"type": "n8n-nodes-base.if",
"typeVersion": 2.2,
"position": [
560,
60
]
},
{
"parameters": {
"resource": "message",
"operation": "post",
"channel": {
"__rl": true,
"value": "#finance-approvals",
"mode": "name"
},
"text": "=:moneybag: *High-Value Invoice Requires Approval*\n\n*Submission ID:* {{ $json.submission_id }}\n*Vendor:* {{ $json.vendor_name }}\n*Invoice #:* {{ $json.invoice_number }}\n*Invoice Date:* {{ $json.invoice_date }}\n*Due Date:* {{ $json.due_date }}\n*Total Amount:* {{ $json.currency }} {{ $json.total_amount.toFixed(2) }}\n*Totals Match:* {{ $json.totals_match ? 'Yes' : 'No \u2014 Review Needed' }}\n{{ $json.needs_review ? '*AI Flag:* ' + $json.review_reason : '' }}\n\nPlease review and approve or reject:\n\u2022 *Approve:* POST to `{{ $json.approval_resume_url }}` with `{\"approved\": true}`\n\u2022 *Reject:* POST to `{{ $json.approval_resume_url }}` with `{\"approved\": false, \"reason\": \"your reason\"}`\n\n*This request expires in 48 hours.*",
"otherOptions": {}
},
"id": "slack-approval-request",
"name": "Slack: Request Approval",
"type": "n8n-nodes-base.slack",
"typeVersion": 2.3,
"position": [
800,
-80
],
"credentials": {
"slackOAuth2Api": {
"name": "<your credential>"
}
}
},
{
"parameters": {
"resume": "webhook",
"options": {
"webhookSuffix": "=invoice-approve-{{ $json.submission_id }}",
"responseData": "firstEntryJson",
"limitWaitTime": true,
"limitType": "afterTimeInterval",
"resumeAmount": 48,
"resumeUnit": "hours"
}
},
"id": "wait-approval",
"name": "Wait for Approval",
"type": "n8n-nodes-base.wait",
"typeVersion": 1.1,
"position": [
1040,
-80
]
},
{
"parameters": {
"conditions": {
"options": {
"caseSensitive": false,
"leftValue": "",
"typeValidation": "strict"
},
"conditions": [
{
"id": "c2",
"leftValue": "={{ $json.body.approved }}",
"rightValue": true,
"operator": {
"type": "boolean",
"operation": "true"
}
}
],
"combinator": "and"
},
"options": {}
},
"id": "if-approved",
"name": "Approved?",
"type": "n8n-nodes-base.if",
"typeVersion": 2.2,
"position": [
1280,
-80
]
},
{
"parameters": {
"operation": "append",
"documentId": {
"__rl": true,
"value": "YOUR_INVOICE_SHEET_ID",
"mode": "id"
},
"sheetName": {
"__rl": true,
"value": "Invoices",
"mode": "list",
"cachedResultName": "Invoices"
},
"columns": {
"mappingMode": "defineBelow",
"value": {
"Submission ID": "={{ $('Validate & Parse Totals').item.json.submission_id }}",
"Vendor Name": "={{ $('Validate & Parse Totals').item.json.vendor_name }}",
"Invoice Number": "={{ $('Validate & Parse Totals').item.json.invoice_number }}",
"Invoice Date": "={{ $('Validate & Parse Totals').item.json.invoice_date }}",
"Due Date": "={{ $('Validate & Parse Totals').item.json.due_date }}",
"Currency": "={{ $('Validate & Parse Totals').item.json.currency }}",
"Subtotal": "={{ $('Validate & Parse Totals').item.json.subtotal }}",
"Tax Amount": "={{ $('Validate & Parse Totals').item.json.tax_amount }}",
"Discount": "={{ $('Validate & Parse Totals').item.json.discount_amount }}",
"Total Amount": "={{ $('Validate & Parse Totals').item.json.total_amount }}",
"Amount Due": "={{ $('Validate & Parse Totals').item.json.amount_due }}",
"Payment Terms": "={{ $('Validate & Parse Totals').item.json.payment_terms }}",
"Line Items Count": "={{ $('Validate & Parse Totals').item.json.line_items_count }}",
"Totals Match": "={{ $('Validate & Parse Totals').item.json.totals_match }}",
"Needs Review": "={{ $('Validate & Parse Totals').item.json.needs_review }}",
"Review Reason": "={{ $('Validate & Parse Totals').item.json.review_reason }}",
"Status": "=Approved",
"Extracted At": "={{ $('Validate & Parse Totals').item.json.extracted_at }}"
},
"schema": []
},
"options": {}
},
"id": "sheets-log-approved",
"name": "Google Sheets: Log Approved",
"type": "n8n-nodes-base.googleSheets",
"typeVersion": 4.5,
"position": [
1520,
-200
],
"credentials": {
"googleSheetsOAuth2Api": {
"name": "<your credential>"
}
}
},
{
"parameters": {
"operation": "append",
"documentId": {
"__rl": true,
"value": "YOUR_INVOICE_SHEET_ID",
"mode": "id"
},
"sheetName": {
"__rl": true,
"value": "Invoices",
"mode": "list",
"cachedResultName": "Invoices"
},
"columns": {
"mappingMode": "defineBelow",
"value": {
"Submission ID": "={{ $('Validate & Parse Totals').item.json.submission_id }}",
"Vendor Name": "={{ $('Validate & Parse Totals').item.json.vendor_name }}",
"Invoice Number": "={{ $('Validate & Parse Totals').item.json.invoice_number }}",
"Invoice Date": "={{ $('Validate & Parse Totals').item.json.invoice_date }}",
"Due Date": "={{ $('Validate & Parse Totals').item.json.due_date }}",
"Currency": "={{ $('Validate & Parse Totals').item.json.currency }}",
"Total Amount": "={{ $('Validate & Parse Totals').item.json.total_amount }}",
"Status": "=Rejected",
"Review Reason": "={{ $json.body.reason || 'Rejected by approver' }}",
"Extracted At": "={{ $('Validate & Parse Totals').item.json.extracted_at }}"
},
"schema": []
},
"options": {}
},
"id": "sheets-log-rejected",
"name": "Google Sheets: Log Rejected",
"type": "n8n-nodes-base.googleSheets",
"typeVersion": 4.5,
"position": [
1520,
40
],
"credentials": {
"googleSheetsOAuth2Api": {
"name": "<your credential>"
}
}
},
{
"parameters": {
"operation": "append",
"documentId": {
"__rl": true,
"value": "YOUR_INVOICE_SHEET_ID",
"mode": "id"
},
"sheetName": {
"__rl": true,
"value": "Invoices",
"mode": "list",
"cachedResultName": "Invoices"
},
"columns": {
"mappingMode": "defineBelow",
"value": {
"Submission ID": "={{ $json.submission_id }}",
"Vendor Name": "={{ $json.vendor_name }}",
"Invoice Number": "={{ $json.invoice_number }}",
"Invoice Date": "={{ $json.invoice_date }}",
"Due Date": "={{ $json.due_date }}",
"Currency": "={{ $json.currency }}",
"Subtotal": "={{ $json.subtotal }}",
"Tax Amount": "={{ $json.tax_amount }}",
"Discount": "={{ $json.discount_amount }}",
"Total Amount": "={{ $json.total_amount }}",
"Amount Due": "={{ $json.amount_due }}",
"Payment Terms": "={{ $json.payment_terms }}",
"Line Items Count": "={{ $json.line_items_count }}",
"Totals Match": "={{ $json.totals_match }}",
"Needs Review": "={{ $json.needs_review }}",
"Review Reason": "={{ $json.review_reason }}",
"Status": "=Auto-Approved (Under $5,000)",
"Extracted At": "={{ $json.extracted_at }}"
},
"schema": []
},
"options": {}
},
"id": "sheets-log-auto",
"name": "Google Sheets: Log Auto-Approved",
"type": "n8n-nodes-base.googleSheets",
"typeVersion": 4.5,
"position": [
800,
200
],
"credentials": {
"googleSheetsOAuth2Api": {
"name": "<your credential>"
}
}
},
{
"parameters": {
"resource": "message",
"operation": "post",
"channel": {
"__rl": true,
"value": "#finance-alerts",
"mode": "name"
},
"text": "=:white_check_mark: *High-Value Invoice Approved & Logged*\n\n*Vendor:* {{ $('Validate & Parse Totals').item.json.vendor_name }}\n*Invoice #:* {{ $('Validate & Parse Totals').item.json.invoice_number }}\n*Amount:* {{ $('Validate & Parse Totals').item.json.currency }} {{ $('Validate & Parse Totals').item.json.total_amount.toFixed(2) }}\n*Due:* {{ $('Validate & Parse Totals').item.json.due_date }}\n\nLogged to Google Sheets for payment processing.",
"otherOptions": {}
},
"id": "slack-high-value-approved",
"name": "Slack: High-Value Approved",
"type": "n8n-nodes-base.slack",
"typeVersion": 2.3,
"position": [
1760,
-200
],
"credentials": {
"slackOAuth2Api": {
"name": "<your credential>"
}
}
},
{
"parameters": {},
"id": "error-trigger",
"name": "Error Trigger",
"type": "n8n-nodes-base.errorTrigger",
"typeVersion": 1,
"position": [
1700,
520
]
},
{
"parameters": {
"resource": "message",
"operation": "post",
"channel": {
"__rl": true,
"value": "#workflow-errors",
"mode": "name"
},
"text": "=:red_circle: *Workflow Error: Invoice Data Extraction*\n\n*Node:* {{ $json.execution.lastNodeExecuted }}\n*Error:* {{ $json.execution.error.message }}\n*Execution ID:* {{ $json.execution.id }}\n*Time:* {{ new Date().toISOString() }}\n\nThe invoice may need to be resubmitted or processed manually.",
"otherOptions": {}
},
"id": "slack-error",
"name": "Slack: Error Alert",
"type": "n8n-nodes-base.slack",
"typeVersion": 2.3,
"position": [
1940,
520
],
"credentials": {
"slackOAuth2Api": {
"name": "<your credential>"
}
}
}
],
"connections": {
"Receive Invoice": {
"main": [
[
{
"node": "OpenAI: Extract Invoice Data",
"type": "main",
"index": 0
}
]
]
},
"OpenAI: Extract Invoice Data": {
"main": [
[
{
"node": "Validate & Parse Totals",
"type": "main",
"index": 0
}
]
]
},
"Validate & Parse Totals": {
"main": [
[
{
"node": "Total > $5,000?",
"type": "main",
"index": 0
}
]
]
},
"Total > $5,000?": {
"main": [
[
{
"node": "Slack: Request Approval",
"type": "main",
"index": 0
}
],
[
{
"node": "Google Sheets: Log Auto-Approved",
"type": "main",
"index": 0
}
]
]
},
"Slack: Request Approval": {
"main": [
[
{
"node": "Wait for Approval",
"type": "main",
"index": 0
}
]
]
},
"Wait for Approval": {
"main": [
[
{
"node": "Approved?",
"type": "main",
"index": 0
}
]
]
},
"Approved?": {
"main": [
[
{
"node": "Google Sheets: Log Approved",
"type": "main",
"index": 0
}
],
[
{
"node": "Google Sheets: Log Rejected",
"type": "main",
"index": 0
}
]
]
},
"Google Sheets: Log Approved": {
"main": [
[
{
"node": "Slack: High-Value Approved",
"type": "main",
"index": 0
}
]
]
},
"Error Trigger": {
"main": [
[
{
"node": "Slack: Error Alert",
"type": "main",
"index": 0
}
]
]
}
},
"settings": {
"executionOrder": "v1",
"saveManualExecutions": true,
"callerPolicy": "workflowsFromSameOwner",
"errorWorkflow": "",
"saveExecutionProgress": true,
"saveDataSuccessExecution": "all",
"saveDataErrorExecution": "all",
"timezone": "America/New_York"
},
"staticData": null,
"tags": [
"invoice",
"finance",
"openai",
"human-approval",
"data-extraction"
],
"triggerCount": 1,
"updatedAt": "2026-05-14T00:00:00.000Z",
"versionId": "06-invoice-extraction-v1",
"active": false,
"id": "workflow-06"
}
Credentials you'll need
Each integration node will prompt for credentials when you import. We strip credential IDs before publishing — you'll add your own.
googleSheetsOAuth2ApihttpHeaderAuthslackOAuth2Api
Pro
For the full experience including quality scoring and batch install features for each workflow upgrade to Pro
About this workflow
Invoice Data Extraction. Uses httpRequest, slack, googleSheets, errorTrigger. Webhook trigger; 16 nodes.
Source: https://github.com/humayun-sarfraz/n8n-ai-workflow-kit/blob/main/workflows/06-invoice-data-extraction.json — original creator credit. Request a take-down →
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