n8n Workflow: Low Stock Purchase Orders via Google Sheets, Slack & OpenAI

Automatically detect low stock, generate Slack purchase orders with OpenAI, and update your inventory—right from Google Sheets

This n8n workflow monitors your Google Sheets inventory, identifies products that are at (or below) their reorder threshold, uses OpenAI to draft a concise purchase order message, and posts reorder notifications to Slack. It then updates your inventory records and logs reorder activity in a dedicated Google Sheets worksheet.

What this workflow does

• Runs manually (or via an optional, disabled 4-hour schedule) and reads all products from your Google Sheets Inventory worksheet.
• Processes products row-by-row: calculates stock percentage, determines an urgency level, computes reorder quantity and estimated cost, and updates the product’s Last Checked date in the sheet.
• Reorder decision logic: if a product is at/below its Reorder Threshold and it hasn’t already been reordered today, the workflow sends product + supplier details to OpenAI to generate a concise purchase order message.
• Slack notifications: posts the generated purchase order message to a designated Slack reorder channel.
• Inventory & audit trail updates: writes the reorder date back to the inventory row, increments Reorder Count, appends a record to Google Sheets Reorder_Log, and posts a completion summary to a Slack summary channel.

Use cases

• SaaS operators who track stock in Google Sheets and want automated reorder alerts in Slack.
• Automation engineers needing an n8n workflow for low stock purchase order generation with an OpenAI-written message.
• Teams that require a reorder log for visibility and basic inventory auditing.

Technical details

• Integrations: Google Sheets, Slack, OpenAI
• n8n nodes used: if, code, slack, google sheets (plus workflow control nodes like an error trigger and sticky notes)
• Setup requirements: add Google Sheets credentials, configure the Inventory and Reorder_Log sheet tabs, and include expected columns (e.g., Product_ID, Current_Stock, Max_Stock, Reorder_Threshold_Pct, supplier details, Last_Reorder_Date, Reorder_Count). Add an OpenAI API key.