Automate E-Signatures with n8n & Webhooks: Low-Code Guide (2026)

// Extract inbound lead and database enrichment items
const lead = $input.first().json;
const items = lead.line_items || [];

// Calculate financial totals and localized tax
const subtotal = items.reduce((acc, item) => acc + (item.quantity * item.unit_price), 0);
const taxRate = lead.tax_exempt ? 0 : 0.20; // 20% standard VAT
const taxAmount = subtotal * taxRate;
const totalAmount = subtotal + taxAmount;

// Format items into clean GFM Markdown Table
const tableRows = items.map(item => 
  `| ${item.name} | ${item.quantity} | $${item.unit_price.toFixed(2)} | $${(item.quantity * item.unit_price).toFixed(2)} |`
).join('\n');

// Conditionally append enterprise SLA clauses based on deal threshold
const enterpriseSlaClause = totalAmount >= 50000 
  ? `
### 4. Enterprise Service Level Agreement (SLA)
- **Availability Commitment:** 99.95% monthly uptime.
- **Priority Support:** 30-minute response SLA for Severity-1 outages.
- **Dedicated Account Executive:** Assigned upon contract execution.
` 
  : `
### 4. Standard Support Terms
- **Availability Commitment:** 99.9% monthly uptime.
- **Standard Support:** 8 business hours response window.
`;

// Compile full agreement markdown
const contractMarkdown = `# Enterprise Master Services Agreement
**Agreement ID:** ${lead.deal_id}  
**Effective Date:** ${new Date().toISOString().split('T')[0]}  
**Provider:** CloudScale Infrastructure Ltd  
**Customer:** ${lead.company_name} (Reg: ${lead.registration_number})  
**Signatory:** ${lead.representative_name} (${lead.representative_email})

---

## 1. Scope of Services & Bill of Materials

The Customer engages CloudScale Infrastructure Ltd to supply the following dedicated resources:

| Item Description | Qty | Unit Price | Total USD |
|:-----------------|:---:|:----------:|:---------:|
${tableRows}

---

| | | **Subtotal:** | **$${subtotal.toFixed(2)}** |
|:---|:---|:---|:---|
| | | **VAT / Tax (${(taxRate * 100).toFixed(0)}%):** | **$${taxAmount.toFixed(2)}** |
| | | **Total Authorized Contract Value:** | **$${totalAmount.toFixed(2)}** |

## 2. Payment Terms
Payment shall be remitted via wire transfer or credit facility within thirty (30) calendar days 
of the execution date. Late payments incur interest at 1.5% per month.

## 3. Intellectual Property & Confidentiality
All customer data hosted within the dedicated infrastructure remains the exclusive property 
of ${lead.company_name}. Both parties agree to preserve strict confidentiality under mutual NDA.

${enterpriseSlaClause}

---

## Authorization & Execution
By signing below, the authorized corporate officer confirms that they hold the legal authority 
to bind ${lead.company_name} to the terms and financial liabilities set forth herein.
`;

return [{
  json: {
    deal_id: lead.deal_id,
    company_name: lead.company_name,
    recipient_name: lead.representative_name,
    recipient_email: lead.representative_email,
    total_amount: totalAmount,
    markdown_content: contractMarkdown
  }
}];

curl -X POST https://signb.ee/api/v1/send \
  -H "Authorization: Bearer {{ $env.SIGNBEE_API_KEY }}" \
  -H "Content-Type: application/json" \
  -d '{
    "title": "Master Services Agreement — " + {{ $json.company_name }},
    "markdown": {{ JSON.stringify($json.markdown_content) }},
    "recipient_name": {{ $json.recipient_name }},
    "recipient_email": {{ $json.recipient_email }},
    "subject": "Action Required: Please review and execute your Master Services Agreement",
    "webhook_url": "https://n8n.yourdomain.com/webhook/signbee-contract-signed"
  }'

{
  "document_id": "cmm8902abc12345678",
  "status": "pending_recipient",
  "sender": "contracts@yourdomain.com",
  "recipient": "Sarah Jenkins",
  "recipient_email": "sarah@acmecorp.com",
  "expires_at": "2026-10-12T12:00:00.000Z",
  "webhook_secret": "whsec_9a8b7c6d5e4f3a2b1c0d9e8f7a6b5c4d"
}

const crypto = require('crypto');

// Retrieve headers and raw body from Webhook Node
const headers = $input.first().json.headers;
const rawBody = $input.first().json.rawBody;
const signatureHeader = headers['x-signbee-signature'];

// Secret configured in workflow credentials or env
const webhookSecret = $env.SIGNBEE_WEBHOOK_SECRET;

if (!signatureHeader || !rawBody) {
  return [{
    json: {
      verified: false,
      reason: "Missing signature header or raw request body"
    }
  }];
}

// Compute expected HMAC SHA-256 hex digest
const computedDigest = crypto
  .createHmac('sha256', webhookSecret)
  .update(rawBody)
  .digest('hex');

// Execute constant-time buffer comparison to prevent timing attacks
const signatureBuffer = Buffer.from(signatureHeader, 'utf8');
const computedBuffer = Buffer.from(computedDigest, 'utf8');

const isValid = signatureBuffer.length === computedBuffer.length && 
  crypto.timingSafeEqual(signatureBuffer, computedBuffer);

if (!isValid) {
  throw new Error("Invalid X-Signbee-Signature. Request verification failed.");
}

// Parse verified body for downstream nodes
const payload = JSON.parse(rawBody);

return [{
  json: {
    verified: true,
    document_id: payload.document_id,
    recipient_email: payload.recipient_email,
    recipient_signed_at: payload.recipient_signed_at,
    signed_pdf_url: payload.signed_pdf_url,
    signature_hash: payload.signature_hash,
    verify_url: payload.verify_url
  }
}];

{
  "name": "Signbee Automated Contract Pipeline (2026)",
  "nodes": [
    {
      "parameters": {
        "httpMethod": "POST",
        "path": "inbound-deal-trigger",
        "options": {}
      },
      "id": "node-1-trigger",
      "name": "Webhook: Inbound Deal",
      "type": "n8n-nodes-base.webhook",
      "typeVersion": 1,
      "position": [180, 240]
    },
    {
      "parameters": {
        "operation": "executeQuery",
        "query": "SELECT company_name, registration_no, credit_status, billing_country FROM enterprise_accounts WHERE id = $1;",
        "additionalFields": {
          "queryParams": "={{ $json.body.account_id }}"
        }
      },
      "id": "node-2-postgres",
      "name": "Postgres: Enrich Account",
      "type": "n8n-nodes-base.postgres",
      "typeVersion": 2.1,
      "position": [380, 240]
    },
    {
      "parameters": {
        "jsCode": "const deal = $input.first().json;\nconst items = deal.line_items || [{ name: 'Standard Platform Access', qty: 1, price: 12000 }];\nconst subtotal = items.reduce((sum, i) => sum + (i.qty * i.price), 0);\nconst rows = items.map(i => `| ${i.name} | ${i.qty} | $${i.price} | $${i.qty * i.price} |`).join('\\n');\n\nconst md = `# Master Services Agreement\\n**Client:** ${deal.company_name} (Reg: ${deal.registration_no})\\n**Signer:** ${deal.signer_name} (${deal.signer_email})\\n\\n| Service | Qty | Rate | Total |\\n|---|---|---|---|\\n${rows}\\n\\n**Total Contract Value:** $${subtotal}\\n\\nBy signing, you agree to 30-day payment terms.`;\n\nreturn [{ json: { recipient_name: deal.signer_name, recipient_email: deal.signer_email, company: deal.company_name, markdown: md } }];"
      },
      "id": "node-3-code-md",
      "name": "Code: Build Markdown",
      "type": "n8n-nodes-base.code",
      "typeVersion": 2,
      "position": [580, 240]
    },
    {
      "parameters": {
        "method": "POST",
        "url": "https://signb.ee/api/v1/send",
        "sendHeaders": true,
        "headerParameters": {
          "parameters": [
            { "name": "Authorization", "value": "Bearer ={{ $env.SIGNBEE_API_KEY }}" },
            { "name": "Content-Type", "value": "application/json" }
          ]
        },
        "sendBody": true,
        "specifyBody": "json",
        "jsonBody": "={\n  \"title\": \"Master Services Agreement - \" + $json.company,\n  \"markdown\": $json.markdown,\n  \"recipient_name\": $json.recipient_name,\n  \"recipient_email\": $json.recipient_email,\n  \"webhook_url\": \"https://n8n.yourdomain.com/webhook/signbee-signature-completed\"\n}"
      },
      "id": "node-4-send-api",
      "name": "HTTP: Signbee Send",
      "type": "n8n-nodes-base.httpRequest",
      "typeVersion": 4.1,
      "position": [780, 240]
    },
    {
      "parameters": {
        "httpMethod": "POST",
        "path": "signbee-signature-completed",
        "responseMode": "onReceived",
        "options": {
          "rawBody": true
        }
      },
      "id": "node-5-webhook-listener",
      "name": "Webhook: document.signed",
      "type": "n8n-nodes-base.webhook",
      "typeVersion": 1,
      "position": [180, 520]
    },
    {
      "parameters": {
        "jsCode": "const crypto = require('crypto');\nconst headers = $input.first().json.headers;\nconst rawBody = $input.first().json.rawBody;\nconst secret = $env.SIGNBEE_WEBHOOK_SECRET;\nconst incomingSig = headers['x-signbee-signature'];\n\nif (!incomingSig || !rawBody) {\n  throw new Error('Unauthorized: Missing signature or body');\n}\n\nconst computed = crypto.createHmac('sha256', secret).update(rawBody).digest('hex');\nconst bufA = Buffer.from(incomingSig, 'utf8');\nconst bufB = Buffer.from(computed, 'utf8');\n\nif (bufA.length !== bufB.length || !crypto.timingSafeEqual(bufA, bufB)) {\n  throw new Error('Forbidden: Invalid HMAC signature');\n}\n\nconst payload = JSON.parse(rawBody);\nreturn [{ json: payload }];"
      },
      "id": "node-6-crypto-verify",
      "name": "Code: Verify HMAC",
      "type": "n8n-nodes-base.code",
      "typeVersion": 2,
      "position": [380, 520]
    },
    {
      "parameters": {
        "resource": "deal",
        "operation": "update",
        "dealId": "={{ $json.document_id }}",
        "updateFields": {
          "stage": "closedwon",
          "customPropertiesUi": {
            "customPropertiesValues": [
              { "property": "contract_signed_at", "value": "={{ $json.recipient_signed_at }}" },
              { "property": "certificate_sha256", "value": "={{ $json.signature_hash }}" },
              { "property": "signed_pdf_url", "value": "={{ $json.signed_pdf_url }}" }
            ]
          }
        }
      },
      "id": "node-7-hubspot",
      "name": "HubSpot: Mark Won",
      "type": "n8n-nodes-base.hubspot",
      "typeVersion": 1,
      "position": [600, 440]
    },
    {
      "parameters": {
        "channel": "#deals-closed",
        "text": "=🚀 Deal Closed! *{{ $json.title }}* was signed by *{{ $json.recipient_name }}* ({{ $json.recipient_email }}).\\n• PDF: {{ $json.signed_pdf_url }}\\n• Certificate SHA-256: `{{ $json.signature_hash }}`"
      },
      "id": "node-8-slack",
      "name": "Slack: Notify Sales",
      "type": "n8n-nodes-base.slack",
      "typeVersion": 2.1,
      "position": [600, 600]
    }
  ],
  "connections": {
    "Webhook: Inbound Deal": {
      "main": [[{ "node": "Postgres: Enrich Account", "type": "main", "index": 0 }]]
    },
    "Postgres: Enrich Account": {
      "main": [[{ "node": "Code: Build Markdown", "type": "main", "index": 0 }]]
    },
    "Code: Build Markdown": {
      "main": [[{ "node": "HTTP: Signbee Send", "type": "main", "index": 0 }]]
    },
    "Webhook: document.signed": {
      "main": [[{ "node": "Code: Verify HMAC", "type": "main", "index": 0 }]]
    },
    "Code: Verify HMAC": {
      "main": [
        [
          { "node": "HubSpot: Mark Won", "type": "main", "index": 0 },
          { "node": "Slack: Notify Sales", "type": "main", "index": 0 }
        ]
      ]
    }
  }
}