Automated AP: Dext Document Extraction to Sage Accounting (n8n)

1. **Establish Webhook Trigger**: Create a 'Webhook Node' in n8n. Set the HTTP Method to POST. Copy the Test URL and paste it into your Dext Partner/Direct account under the Webhook settings for 'Item Published'. 2. **Configure Credentials**: For Dext, use a 'Header Auth' or 'Secret' node if using an API Key. For Sage, create an 'OAuth2 Credentials' object in n8n (using Client ID, Secret, and Auth/Token URLs specific to your Sage region). 3. **Data Polling/Fetching**: While the webhook initiates the flow, use an 'HTTP Request Node' to fetch the full JSON of the item from the Dext `/items` endpoint using the `item_id` from the webhook payload. 4. **Standardize Dates**: Use an 'Expression' in a Set Node or Code Node to format the Dext `date` field. Sage requires `YYYY-MM-DD`. Use: `{{ DateTime.fromISO($json.date).toISODate() }}`. 5. **Look up Sage Vendor**: Add an 'HTTP Request Node' to Sage's `/contacts` endpoint to find the vendor matching the Dext `supplier_name`. If not found, use an 'IF Node' to route to a 'Create Contact' node. 6. **Map Line Items**: Use the 'Code Node' or 'Item Lists' node to iterate through Dext's `line_items` array. Map Dext's `tax_amount` and `description` to the corresponding Sage JSON structure. 7. **Handle Attachments**: Use an 'HTTP Request Node' with the Dext `image_url`. In the node settings, change 'Response Format' to 'File'. This allows n8n to hold the binary data in memory for the next step. 8. **Post to Sage**: Use another 'HTTP Request Node' (POST) to the Sage `/purchase_invoices` endpoint. In the 'Body Parameters', reference the mapped expressions from previous steps. 9. **Attach PDF/Image**: Use the Sage `/attachments` endpoint. Pass the binary data from step 7. Ensure you link the `attachment_id` to the Invoice ID created in step 8. 10. **Error Handling**: Create an 'Error Trigger' workflow or use the 'On Error' settings on the Sage nodes to catch API rate limits (429) or validation errors (400), sending them to a 'Sticky Note' or Slack channel.

| Dext Field | Sage Field | n8n Expression / Transformation | | :--- | :--- | :--- | | `supplier_name` | `contact_id` | Match via `HTTP Request` GET and `{{$json.id}}` | | `date` | `date` | `{{ DateTime.fromISO($node.Dext.json.date).toISODate() }}` | | `net_amount` | `net_amount` | `{{ $json.net_amount.toFloat() }}` | | `tax_amount` | `tax_amount` | `{{ $json.tax_amount.toFloat() }}` | | `reference` | `reference` | `{{ $json.reference || 'N/A' }}` | | `category` | `ledger_account_id` | Use a `Static Mapping Table` or `Switch Node` | | `image_url` | `attachment` | Manual binary fetch via HTTP Request node |

- **Rate Limiting**: Sage APIs often limit requests per minute. Use the n8n 'Wait' node or 'Split in Batches' if publishing multiple items at once. - **Binary Memory**: If processing large PDF invoices, ensure your n8n instance has sufficient RAM, as binary data is handled in-memory by default. - **Tax Code Mismatches**: Sage is very strict about tax rates. Use an n8n 'Switch' node to map Dext tax labels (e.g., '20% VAT') to Sage Tax IDs (e.g., 'GB_VAT_REDUCED'). - **OAuth Token Expiry**: Ensure n8n is configured to automatically refresh the Sage OAuth token; otherwise, the workflow will fail after 60 minutes of inactivity.

- [ ] Webhook successfully receives `item_id` from Dext. - [ ] Date format verified as `YYYY-MM-DD` in the n8n execution log. - [ ] Sage Vendor lookup returns a valid UUID or ID string. - [ ] Attachment binary shows as a 'Binary' tab in the n8n node execution output. - [ ] Purchase Invoice appears in Sage as 'Draft' or 'Pending'. - [ ] Error handler triggers a notification if the Sage API returns a 400 'Balance Mismatch'.