Gmail to GSTR-2B GST Reconciliation in Google Sheets (OpenAI + n8n)

Automatically reconcile Gmail purchase invoices with GSTR-2B in Google Sheets (OpenAI + n8n)

This Gmail to GSTR-2B GST Reconciliation workflow pulls GST invoice PDFs from your Gmail, extracts invoice details using OpenAI, compares them against your GSTR-2B data in Google Sheets, and produces an ITC-at-risk summary—plus vendor follow-ups as Gmail drafts.

What this workflow does

• Runs monthly: Scheduled for 10:00 AM on the 15th to set company details, the return period, tax tolerance, and a Gmail search query.
• Searches Gmail and processes invoice PDFs: Finds relevant messages, downloads PDF attachments, and splits each invoice PDF into a separate item while keeping sender/thread context.
• Extracts invoice fields with OpenAI: Reads each PDF and parses key fields such as GSTINs, invoice number/date, taxable value, and IGST/CGST/SGST. It skips non-tax invoices and avoids duplicates.
• Reconciles against GSTR-2B: Matches by supplier GSTIN and invoice number, with a fallback match on tax amounts within the configured tolerance.
• Flags issues and gaps: Identifies missing invoices in GSTR-2B, tax mismatches, invalid supplier GSTINs, invoices billed to the wrong buyer GSTIN, and any GSTR-2B entries with no matching invoice email.
• Writes results and emails a summary: Appends/updates a Google Sheets “Reconciliation” tab, then emails an HTML summary to accounts with counts and total ITC at risk.
• Creates vendor reminders: Groups flagged items by vendor, uses OpenAI to draft a concise reminder per vendor, and saves each as a Gmail draft.

Use cases

• Monthly GST operations: reconcile purchase invoices automatically against GSTR-2B.
• Reduce ITC risk by quickly identifying mismatches and missing supplier reporting.
• Generate vendor follow-up communication drafts without manual drafting.

Technical details

• Automation platform: n8n workflow automation
• Integrations/nodes: if, set, code, gmail, filter, sticky note
• AI extraction: OpenAI for parsing GST invoice PDFs
• Data source: Google Sheets “GSTR-2B” tab and a reconciliation output tab