{"product_id":"automate-supplier-invoice-processing-with-document-ai-accounting-api-slack","title":"Automate Supplier Invoice Processing with Document AI, Accounting API \u0026 Slack","description":"\u003ch3\u003eAutomate Supplier Invoice Processing end-to-end with Document AI, Accounting API validation, and Slack alerts\u003c\/h3\u003e\n\u003cp\u003eThis n8n workflow receives supplier invoices via webhook, extracts invoice data using a document extraction endpoint, validates the results against supplier and open purchase orders from an accounting REST API, and then auto-posts approved bills, queues exceptions for review, or sends rejection alerts via Slack.\u003c\/p\u003e\n\n\u003ch3\u003eWhat this workflow does\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eIngest invoices via webhook\u003c\/strong\u003e: Accepts an invoice payload from your backend-connected source (e.g., email\/Drive\/upload) through an n8n \u003cstrong\u003ewebhook\u003c\/strong\u003e trigger.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eExtract invoice fields\u003c\/strong\u003e: Calls a REST endpoint (e.g., \u003ccode\u003e\/documents\/extract\u003c\/code\u003e) to extract supplier, TRN, invoice number, totals, confidence, and line items.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eValidate against accounting data\u003c\/strong\u003e: Fetches supplier master data and open purchase orders from an accounting REST API (e.g., \u003ccode\u003e\/accounting\/suppliers\u003c\/code\u003e and \u003ccode\u003e\/accounting\/purchase_orders\u003c\/code\u003e), then checks rules including:\n    \u003cul\u003e\n      \u003cli\u003eDuplicate invoice number\u003c\/li\u003e\n      \u003cli\u003eTRN format and TRN match\u003c\/li\u003e\n      \u003cli\u003eLine totals vs subtotal\u003c\/li\u003e\n      \u003cli\u003eTotal vs subtotal plus VAT\u003c\/li\u003e\n      \u003cli\u003eConfidence threshold\u003c\/li\u003e\n      \u003cli\u003ePO match and approval limits\u003c\/li\u003e\n    \u003c\/ul\u003e\n  \u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRoute the outcome\u003c\/strong\u003e: Automatically \u003cem\u003eapprove\u003c\/em\u003e, send to \u003cem\u003ereview\u003c\/em\u003e, or \u003cem\u003ereject\u003c\/em\u003e based on validation results.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAct and respond\u003c\/strong\u003e: Posts approved bills to \u003ccode\u003e\/accounting\/bills\u003c\/code\u003e, creates review items in \u003ccode\u003e\/review\/queue\u003c\/code\u003e, or triggers rejection alerts via an alerts endpoint (Slack-backed). Returns a \u003cstrong\u003e200 JSON\u003c\/strong\u003e response with the outcome.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eUse cases\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003eReduce manual AP work by auto-processing invoices that match an existing PO and pass validation.\u003c\/li\u003e\n  \u003cli\u003eCatch data issues early (VAT\/total mismatches, duplicate invoice numbers, low confidence extraction) and route them to a review queue.\u003c\/li\u003e\n  \u003cli\u003eImprove supplier compliance by validating TRN format and match before posting bills to your accounting system.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eTechnical details\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHTTP endpoints\u003c\/strong\u003e: Document extraction (\u003ccode\u003e\/documents\/extract\u003c\/code\u003e), accounting REST API (suppliers, purchase orders, bills), review queue (\u003ccode\u003e\/review\/queue\u003c\/code\u003e), and alerts.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSlack\u003c\/strong\u003e: Used to send rejection alerts for invalid invoices.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003en8n nodes\u003c\/strong\u003e: \u003cstrong\u003ewebhook\u003c\/strong\u003e, \u003cstrong\u003eset\u003c\/strong\u003e, \u003cstrong\u003ecode\u003c\/strong\u003e, \u003cstrong\u003emerge\u003c\/strong\u003e, and \u003cstrong\u003eswitch\u003c\/strong\u003e for routing logic (plus supporting \u003cstrong\u003esticky note\u003c\/strong\u003e documentation).\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSetup requirement\u003c\/strong\u003e: Provide a reachable \u003cstrong\u003eHTTPS base URL\u003c\/strong\u003e for your backend APIs and update it in the Config and Config (errors) steps.\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"N8N Commerce","offers":[{"title":"Default Title","offer_id":46029569196211,"sku":"N8N-19573","price":63.99,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0749\/6279\/6723\/files\/vJOQhOakWNLhRv6pp4FN7_FXT8LrAC.png?v=1789464140","url":"https:\/\/buyflowscripts.com\/products\/automate-supplier-invoice-processing-with-document-ai-accounting-api-slack","provider":"N8N Commerce","version":"1.0","type":"link"}