{"product_id":"detect-duplicate-supplier-invoices-in-google-sheets-slack-alerts","title":"Detect Duplicate Supplier Invoices in Google Sheets (Slack Alerts)","description":"\u003ch3\u003eStop paying the same supplier invoice twice — Detect duplicates in Google Sheets and notify your team on Slack\u003c\/h3\u003e\n\u003cp\u003eThis n8n workflow runs every weekday morning to scan your supplier invoice Google Sheet, identify invoice pairs that appear to be duplicates (or the “same bill under a new number”), and post the results to Slack for review.\u003c\/p\u003e\n\n\u003ch3\u003eWhat this workflow does\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cb\u003eScheduled check:\u003c\/b\u003e A schedule trigger runs at \u003cb\u003e08:00 on weekdays\u003c\/b\u003e.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cb\u003eReads your invoice tab once:\u003c\/b\u003e The workflow pulls invoice rows from your Google Sheets invoice tab.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cb\u003eNormalizes supplier names and invoice numbers:\u003c\/b\u003e Supplier names are tidied (e.g., “Ltd”, “Limited”, and punctuation differences are ignored). Invoice numbers are compared in a way that treats \u003cb\u003e“INV-000123” as matching “123”\u003c\/b\u003e.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cb\u003eDetects likely duplicate pairs:\u003c\/b\u003e For the same supplier, it flags pairs when they match by:\n    \u003cul\u003e\n      \u003cli\u003e\u003cb\u003eSame invoice number + same amount\u003c\/b\u003e\u003c\/li\u003e\n      \u003cli\u003e\u003cb\u003eSame invoice number + different amount\u003c\/b\u003e\u003c\/li\u003e\n      \u003cli\u003e\u003cb\u003eSame amount under a new invoice number within a \u003cb\u003e45-day\u003c\/b\u003e window\u003c\/b\u003e\u003c\/li\u003e\n    \u003c\/ul\u003e\n  \u003c\/li\u003e\n  \u003cli\u003e\n\u003cb\u003eRescans safely:\u003c\/b\u003e Any pair already present in your \u003cb\u003ePossible duplicates\u003c\/b\u003e tab is skipped, so previously reviewed items aren’t re-raised tomorrow.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cb\u003eWrites new findings:\u003c\/b\u003e New pairs are added to the \u003cb\u003ePossible duplicates\u003c\/b\u003e tab and sent as a single \u003cb\u003eSlack\u003c\/b\u003e message listing them.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eUse cases\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003ePrevents duplicate payments before your payment run.\u003c\/li\u003e\n  \u003cli\u003eHelps accounts payable teams catch revised invoice numbers and amount changes within a month.\u003c\/li\u003e\n  \u003cli\u003eReduces manual searching by centralizing review in a “Possible duplicates” Google Sheets tab and Slack alerts.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eTechnical details\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cb\u003eIntegrations:\u003c\/b\u003e \u003cb\u003eGoogle Sheets\u003c\/b\u003e and \u003cb\u003eSlack\u003c\/b\u003e\n\u003c\/li\u003e\n  \u003cli\u003e\n\u003cb\u003en8n nodes\/blocks:\u003c\/b\u003e \u003ccode\u003eschedule trigger\u003c\/code\u003e, \u003ccode\u003egoogle sheets\u003c\/code\u003e, \u003ccode\u003ecode\u003c\/code\u003e, \u003ccode\u003eset\u003c\/code\u003e, \u003ccode\u003eslack\u003c\/code\u003e, and a \u003ccode\u003esticky note\u003c\/code\u003e for setup guidance\u003c\/li\u003e\n  \u003cli\u003e\n\u003cb\u003eSetup requirements:\u003c\/b\u003e Add the \u003cb\u003ePossible duplicates\u003c\/b\u003e tab with the required 11 headers; paste your sheet URL in \u003cb\u003eSettings\u003c\/b\u003e; configure the four column names to match your invoice tab.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eIf the workflow flags too many pairs, you can lower \u003cb\u003edateWindowDays\u003c\/b\u003e.\u003c\/p\u003e","brand":"N8N Commerce","offers":[{"title":"Default Title","offer_id":46248929591475,"sku":"N8N-21186","price":65.99,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0749\/6279\/6723\/files\/KDMr0I4hFGFa6nu1oj0Mn_oTMqDrn1.png?v=1792487615","url":"https:\/\/buyflowscripts.com\/products\/detect-duplicate-supplier-invoices-in-google-sheets-slack-alerts","provider":"N8N Commerce","version":"1.0","type":"link"}