Slack Receipt Approval to Xero Invoice with Textract & OpenAI

Automatically turn Slack receipt images into approved Xero ACCPAY invoices—using AWS Textract and OpenAI

This n8n workflow captures expense receipt files shared in Slack, extracts vendor and totals with AWS Textract, confirms and categorizes them with OpenAI, pauses for manager approval in Slack, and then creates an authorised ACCPAY invoice in Xero with the receipt attached—while logging outcomes to Google Sheets.

What this workflow does

• Triggers on Slack file shares and downloads the shared attachment.
• Filters receipt uploads and sends receipt images to AWS Textract AnalyzeExpense to extract vendor, total, date, and currency.
• Uses OpenAI for expense categorization, assigning a single category from a fixed list and normalizing extracted fields while checking Textract confidence thresholds.
• If extraction confidence is low, it posts a Slack message asking the uploader to resend a clearer photo.
• If extraction confidence is high, it posts a Slack approval request and pauses until a manager approves or rejects.
• On approval: maps the category to a Xero account code, creates an authorised Xero ACCPAY invoice via the workflow’s Xero API routing, reattaches the original receipt image as an invoice attachment, and appends an “approved” entry to Google Sheets.
• On rejection: notifies the original Slack user and appends a “rejected” entry to Google Sheets.

Use cases

• Expense processing for teams that submit receipts in Slack.
• Approval workflows where invoices must be authorised in Xero ACCPAY only after manager review.
• Reducing manual data entry by extracting receipt fields with AWS Textract and categorizing with OpenAI.

Technical details

• Slack (file_share handling, messaging, interactive approvals)
• AWS Textract (AnalyzeExpense extraction)
• OpenAI (category assignment from a fixed list)
• Xero (creates authorised ACCPAY invoices + receipt attachment; routing via two API request paths)
• Google Sheets (logs approved/rejected outcomes)
• n8n nodes: if, filter, code, switch, OpenAI, Slack