Detect SaaS Subscription Leaks: n8n Google Drive + Gmail

Detect SaaS subscription leaks automatically—using your Google Drive, Gmail, and inventory data

This n8n workflow audits SaaS spend by combining corporate card CSVs from Google Drive, invoice/receipt emails from Gmail (parsed with OpenAI), and your SaaS Inventory in Google Sheets. It then flags likely subscription waste and generates a prioritized cancellation/optimization plan—delivered to Google Sheets, email, and Slack.

What this workflow does

• Runs weekly or on-demand: Manual trigger or every Monday at 9 AM, loading configuration values (folder IDs, Google Sheet ID, thresholds, report email, and Slack channel).
• Parses corporate card statements: Pulls statement CSV files from Google Drive, downloads them, normalizes rows into consistent charge records.
• Extracts SaaS invoice line items from Gmail: Fetches recent invoice/receipt emails, batches them, and uses OpenAI (gpt-4o-mini) to extract structured SaaS invoice details.
• Cross-references multiple sources: Merges card charges, extracted invoice data, and the “SaaS Inventory” tab in Google Sheets.
• Detects subscription leaks: Flags issues such as zombie charges, duplicate charges, unused tools, seat waste, price increases, overlapping tools, and shadow subscriptions, calculating potential monthly and annual savings.
• Reports only when needed: If leaks are found, generates a prioritized cancellation/optimization plan and sends an HTML report via Gmail and a summary to Slack. If none are found, it ends without sending reports.

Use cases

• Weekly SaaS spend audits for automation engineers managing budgets across tools and vendors.
• Detecting shadow subscriptions and duplicate billing when teams change seats or renewals.
• Quarterly optimization reporting with prioritized cancellation guidance.

Technical details

• Integrations: Google Drive, Gmail, Google Sheets, Slack
• AI extraction: OpenAI (gpt-4o-mini) for invoice/receipt line-item extraction and plan generation
• n8n node approach: if, set, code, no op, gmail, merge (plus Google credential setup via OAuth2)