n8n LINE Receipt Photo to Google Sheets with OpenAI

Turn LINE receipt photos into a Google Sheets expense log—automatically

This n8n workflow watches for receipt images sent via LINE, uses OpenAI to extract structured expense data, and then appends or updates the row in Google Sheets. It also responds back in LINE with a confirmation—or an error if something goes wrong.

What this workflow does

• Receives a webhook from the LINE Messaging API and checks whether the incoming event contains an image message.
• If the message isn’t an image, it replies in LINE asking the user to send a receipt photo.
• Downloads the receipt image via the LINE content API and converts it to Base64.
• Sends the image to OpenAI Chat Completions with a strict JSON schema to extract: date, store, category, amount, currency, and memo.
• Validates and sanitizes extracted fields (date and currency formats, allowed categories, non-negative amount, and formula-safe text).
• Uses the LINE message ID as a “Receipt ID” to prevent duplicates by appending or updating the Google Sheets row accordingly.
• Replies in LINE with the logged details, or returns a processing error if any step fails.

Use cases

• Capture business expenses instantly by sending a receipt to your LINE Official Account.
• Keep a continuously updated expense log in Google Sheets without manual data entry.
• Use the Receipt ID to safely reprocess messages without creating duplicate rows.

Technical details

• n8n nodes/logic: webhook, if, set, code, sticky note, HTTP request
• Integrations: LINE Messaging API (webhook + content download + LINE replies), OpenAI (Chat Completions with JSON schema), Google Sheets
• Auth: LINE channel access token via HTTP header Authorization: Bearer <token>