n8n Invoice 3-Way Match: Google Sheets + Groq Llama + Notion

Automatically three-way match invoices in Google Sheets—using AI when needed

This n8n workflow performs daily 3-way matching for invoices against Purchase Orders and Goods Receipts stored in Google Sheets, approving confident matches, rejecting uncertain ones with Gmail alerts, and escalating borderline cases to a Notion-backed AI audit powered by Groq Llama 3.3.

What this workflow does

• Runs on a schedule: triggers every day to pull Purchase Order, Goods Receipt, and Invoice rows from Google Sheets.
• Targets only actionable invoices: processes invoices where status is pending and invoice amount > 0.
• Normalizes item descriptions, then finds the best PO/GRN combination for the same vendor.
• Calculates match score using hybrid token similarity + Levenshtein similarity, with a 5% amount tolerance check.
• Approves automatically when scores are high: updates status and match score in Google Sheets and logs the approval to a Notion database.
• Rejects automatically when scores are low: updates Google Sheets, sends a rejection email via Gmail (including score and reason), and archives the case to Notion.
• AI confirms mid-range matches: uses Groq Llama 3.3 semantic checks to confirm whether items refer to the same product—either approving or escalating.
• Escalated AI audit: retrieves past approved transactions for the vendor from Notion, asks Llama 3.3 for a JSON decision (approved/review/rejected), syncs the final status back to Google Sheets, and archives the decision to Notion.

Use cases

• Reduce manual AP workload by automatically matching invoices to PO/GRN data in Google Sheets.
• Send standardized rejection emails when item/amount mismatches fall below acceptable thresholds.
• Use AI review for ambiguous product descriptions while keeping a Notion audit trail.

Technical details

• Integrations/Nodes: if, set, code, gmail, notion, switch.
• Core systems: Google Sheets (data in/out), Gmail (rejection alerts), Notion (logging + vendor history), Groq Llama 3.3 (semantic confirmation + JSON audit decision).
• Setup requirement: add Google Sheets OAuth credentials.