AI Invoice OCR Anomaly Detection

The workflow JSON

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{
  "name": "27-ai-invoice-ocr-anomaly-detection",
  "nodes": [
    {
      "parameters": {
        "httpMethod": "POST",
        "path": "invoice-upload",
        "responseMode": "lastNode",
        "options": {}
      },
      "id": "g7h8i9j0-1111-4444-8888-000000000001",
      "name": "Webhook",
      "type": "n8n-nodes-base.webhook",
      "typeVersion": 2,
      "position": [
        240,
        400
      ]
    },
    {
      "parameters": {
        "model": "gpt-4o",
        "prompt": {
          "messages": [
            {
              "role": "system",
              "content": "You are an expert Financial AI Auditor. Analyze the provided invoice text. Extract: vendor_name, invoice_number, po_number, total_amount, and items (array of {description, amount}). ALSO, perform Anomaly Detection: check if the sum of items matches total_amount, if the date is in the future, or if the vendor name looks suspicious. Respond ONLY in valid JSON format with these exact keys: 'vendor_name', 'invoice_number', 'po_number', 'total_amount', 'items_sum', 'ai_anomaly_detected' (boolean), 'anomaly_reason' (string, or 'None' if valid)."
            },
            {
              "role": "user",
              "content": "Invoice Text Data:\n{{ $json.invoice_text }}"
            }
          ]
        },
        "options": {
          "responseFormat": "json_object"
        }
      },
      "id": "g7h8i9j0-2222-4444-8888-000000000002",
      "name": "OpenAI: OCR & Anomaly Check",
      "type": "n8n-nodes-base.openAi",
      "typeVersion": 1.2,
      "position": [
        460,
        400
      ],
      "credentials": {
        "openAiApi": {
          "name": "<your credential>"
        }
      }
    },
    {
      "parameters": {
        "operation": "executeQuery",
        "query": "SELECT COUNT(*) as dup_count FROM processed_invoices WHERE invoice_number = '{{ JSON.parse($json.content).invoice_number }}';",
        "options": {}
      },
      "id": "g7h8i9j0-3333-4444-8888-000000000003",
      "name": "PostgreSQL: Check Duplicate",
      "type": "n8n-nodes-base.postgres",
      "typeVersion": 2.5,
      "position": [
        680,
        400
      ],
      "credentials": {
        "postgres": {
          "name": "<your credential>"
        }
      }
    },
    {
      "parameters": {
        "jsCode": "// \u0645\u0646\u0637\u0642 \u0646\u0647\u0627\u06cc\u06cc \u062a\u0635\u0645\u06cc\u0645\u200c\u06af\u06cc\u0631\u06cc \u0648 \u0627\u0639\u062a\u0628\u0627\u0631\u0633\u0646\u062c\u06cc\nconst aiResult = JSON.parse($node['OpenAI: OCR & Anomaly Check'].json.content);\nconst dbResult = $input.first().json;\nconst dupCount = parseInt(dbResult.dup_count || 0);\n\nlet finalStatus = 'approved';\nlet rejectionReason = 'None';\n\n// 1. \u0628\u0631\u0631\u0633\u06cc \u062a\u06a9\u0631\u0627\u0631\u06cc \u0628\u0648\u062f\u0646\nif (dupCount > 0) {\n  finalStatus = 'flagged';\n  rejectionReason = 'Duplicate invoice number detected in database.';\n}\n// 2. \u0628\u0631\u0631\u0633\u06cc \u0646\u0627\u0647\u0646\u062c\u0627\u0631\u06cc \u0647\u0648\u0634 \u0645\u0635\u0646\u0648\u0639\u06cc\nelse if (aiResult.ai_anomaly_detected === true) {\n  finalStatus = 'flagged';\n  rejectionReason = `AI Anomaly: ${aiResult.anomaly_reason}`;\n}\n// 3. \u0628\u0631\u0631\u0633\u06cc \u0631\u06cc\u0627\u0636\u06cc \u0633\u0627\u062f\u0647 (\u0627\u062e\u062a\u06cc\u0627\u0631\u06cc\u060c \u0627\u06af\u0631 AI \u0627\u0646\u062c\u0627\u0645 \u0646\u062f\u0627\u062f\u0647 \u0628\u0627\u0634\u062f)\nelse if (Math.abs(aiResult.items_sum - aiResult.total_amount) > 0.01) {\n  finalStatus = 'flagged';\n  rejectionReason = `Math mismatch: Items sum (${aiResult.items_sum}) does not equal Total (${aiResult.total_amount}).`;\n}\n\nreturn [{\n  json: {\n    vendor_name: aiResult.vendor_name,\n    invoice_number: aiResult.invoice_number,\n    po_number: aiResult.po_number,\n    total_amount: aiResult.total_amount,\n    final_status: finalStatus,\n    rejection_reason: rejectionReason,\n    ai_anomaly_detected: aiResult.ai_anomaly_detected\n  }\n}];"
      },
      "id": "g7h8i9j0-4444-4444-8888-000000000004",
      "name": "Code: Final Validation",
      "type": "n8n-nodes-base.code",
      "typeVersion": 2,
      "position": [
        900,
        400
      ]
    },
    {
      "parameters": {
        "rules": {
          "values": [
            {
              "conditions": {
                "options": {
                  "caseSensitive": true,
                  "leftValue": "",
                  "typeValidation": "strict"
                },
                "conditions": [
                  {
                    "id": "c1",
                    "leftValue": "={{ $json.final_status }}",
                    "rightValue": "approved",
                    "operator": {
                      "type": "string",
                      "operation": "equals"
                    }
                  }
                ]
              }
            }
          ]
        },
        "options": {
          "fallbackOutput": "default"
        }
      },
      "id": "g7h8i9j0-5555-4444-8888-000000000005",
      "name": "Switch: Routing",
      "type": "n8n-nodes-base.switch",
      "typeVersion": 3,
      "position": [
        1120,
        400
      ]
    },
    {
      "parameters": {
        "operation": "executeQuery",
        "query": "INSERT INTO processed_invoices (vendor_name, invoice_number, po_number, total_amount, status, processed_at) VALUES ('{{ $json.vendor_name }}', '{{ $json.invoice_number }}', '{{ $json.po_number }}', {{ $json.total_amount }}, 'APPROVED', NOW());",
        "options": {}
      },
      "id": "g7h8i9j0-6666-4444-8888-000000000006",
      "name": "PostgreSQL: Insert Approved",
      "type": "n8n-nodes-base.postgres",
      "typeVersion": 2.5,
      "position": [
        1340,
        320
      ],
      "credentials": {
        "postgres": {
          "name": "<your credential>"
        }
      }
    },
    {
      "parameters": {
        "select": "channel",
        "channelId": {
          "__rl": true,
          "value": "C2222333344",
          "mode": "list",
          "cachedResultName": "finance-alerts"
        },
        "text": "\ud83d\udea8 *INVOICE FLAGGED FOR REVIEW* \ud83d\udea8\n\n\ud83c\udfe2 *Vendor:* {{ $json.vendor_name }}\n\ud83e\uddfe *Invoice #:* {{ $json.invoice_number }}\n\ud83d\udcb0 *Amount:* ${{ $json.total_amount }}\n\u274c *Reason:* {{ $json.rejection_reason }}\n\n\ud83d\udd17 Action Required: Please review in the Finance Dashboard.",
        "otherOptions": {}
      },
      "id": "g7h8i9j0-7777-4444-8888-000000000007",
      "name": "Slack: Finance Alert",
      "type": "n8n-nodes-base.slack",
      "typeVersion": 2.2,
      "position": [
        1340,
        480
      ],
      "credentials": {
        "slackApi": {
          "name": "<your credential>"
        }
      }
    },
    {
      "parameters": {
        "operation": "executeQuery",
        "query": "INSERT INTO audit_log (invoice_number, action_taken, reason, timestamp) VALUES ('{{ $json.invoice_number }}', 'FLAGGED', '{{ $json.rejection_reason }}', NOW());",
        "options": {}
      },
      "id": "g7h8i9j0-8888-4444-8888-000000000008",
      "name": "PostgreSQL: Audit Log",
      "type": "n8n-nodes-base.postgres",
      "typeVersion": 2.5,
      "position": [
        1560,
        480
      ],
      "credentials": {
        "postgres": {
          "name": "<your credential>"
        }
      }
    }
  ],
  "connections": {
    "Webhook": {
      "main": [
        [
          {
            "node": "OpenAI: OCR & Anomaly Check",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "OpenAI: OCR & Anomaly Check": {
      "main": [
        [
          {
            "node": "PostgreSQL: Check Duplicate",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "PostgreSQL: Check Duplicate": {
      "main": [
        [
          {
            "node": "Code: Final Validation",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "Code: Final Validation": {
      "main": [
        [
          {
            "node": "Switch: Routing",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "Switch: Routing": {
      "main": [
        [
          {
            "node": "PostgreSQL: Insert Approved",
            "type": "main",
            "index": 0
          }
        ],
        [
          {
            "node": "Slack: Finance Alert",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "Slack: Finance Alert": {
      "main": [
        [
          {
            "node": "PostgreSQL: Audit Log",
            "type": "main",
            "index": 0
          }
        ]
      ]
    }
  },
  "active": false,
  "settings": {
    "executionOrder": "v1",
    "saveManualExecutions": true,
    "saveDataErrorExecution": "all",
    "saveDataSuccessExecution": "all"
  },
  "id": "27-ai-invoice-ocr-anomaly-detection",
  "tags": []
}

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.

• openAiApi
• postgres
• slackApi

About this workflow

27-ai-invoice-ocr-anomaly-detection. Uses openAi, postgres, slack. Webhook trigger; 8 nodes.

Source: https://github.com/kooroosh1363/agentic-automation-lab/blob/main/27-ai-invoice-ocr-anomaly-detection/workflow.json — original creator credit. Request a take-down →

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