Invoice Payment Timing Automation with n8n, Slack & Google Sheets

Automatically decide invoice payment timing with n8n—then alert your team in Slack and log every recommendation in Google Sheets

This n8n workflow helps you review invoices weekly, compare them against your cash flow snapshot, and recommend whether to pay early or pay on the due date. It also generates a business-friendly explanation using a Groq-hosted LLM, posts “Pay Early” alerts to Slack, and stores the results back in Google Sheets for tracking.

What this workflow does

• Runs weekly via a schedule trigger.
• Reads invoice data from Google Sheets and cash flow metrics (AvailableCash, MinimumReserve, and ForecastedOutflow) from a cash flow snapshot sheet.
• Scores each invoice by combining the invoice row with cash metrics to determine whether the recommended action is Pay Early or Pay On Due Date.
• Calculates key cash impacts including the discount value and projected remaining cash after payment, then produces a decision score.
• Sends the invoice and decision details to a Groq LLM agent to generate an explanation and one risk statement—without changing the provided numbers.
• If the recommendation is Pay Early, posts an alert to Slack with the key details and the AI summary.
• Appends every recommendation (recommendation, reason, cash metrics, and AI summary) to a Google Sheets output tab named Store Recommendation.

Use cases

• Weekly AP review for teams using n8n and Google Sheets to manage invoice timing and discounts.
• Operations/SaaS finance workflow: detect which invoices can be paid early without violating minimum reserves.
• Audit-friendly tracking: maintain a historical log of invoice recommendations and LLM rationales in Google Sheets.

Technical details

• Integrations: Google Sheets, Slack, Groq (LLM).
• n8n nodes mentioned: if, set, code, merge, slack, and a sticky note.
• Setup requirements: provide Google Sheets credentials, map expected columns (e.g., InvoiceID, SupplierName, InvoiceAmount, DiscountPercent, SupplierPriority, and cash fields), and add a Groq API credential.