Automating Accounts Payable with n8n & UiPath
Hybrid purchase-to-pay automation: n8n orchestrates email intake, OCR, validation, and approvals, while UiPath posts the verified invoice data into an ERP without a usable API straight through the desktop screen. Designed and built by Groenewold IT Solutions in Leer/East Frisia (Made in Germany).
Automating Accounts Payable with n8n & UiPath
Automation
The Challenge
Modern SaaS world meets an ERP without an interface
Invoices arrived as PDF attachments, scans from the mailroom, and occasionally on paper. The real obstacle was the target system: an older ERP with no usable REST API, where every posting was typed manually into input masks. A pure OCR or workflow tool would have read the data but left the last mile into the legacy system unsolved.
Double entry, lost cash discounts, missing audit trail
Finance re-checked amounts, vendors, and cost centres; deviations from the purchase order caused back-and-forth and delays. Cash discounts were lost because invoices were posted too late. At the same time, auditors needed a traceable trail: who approved up to which amount, and when did each document reach the ERP?
Our Solution
Workflow and RPA views
n8n as the orchestration layer for the API world
An n8n workflow watches a central mailbox via IMAP trigger, splits off attachments, and sends PDFs to OCR and AI-assisted extraction. n8n validates IBAN and VAT IDs against vendor master data, detects duplicates, and routes anything unclear to an approval in Slack or Microsoft Teams. Only once the record is complete and approved does n8n hand it on.
UiPath as the last mile into the legacy system
For the API-less ERP, a UiPath robot performs the guided entry: it logs in, navigates the posting screen, fills in the verified fields provided by n8n, and files the original PDF in the document management system. This creates an end-to-end chain without touching or expensively re-integrating the grown system. We also explain this split of roles in the RPA vs API integration comparison.
Engineering from East Frisia
Design and delivery were led by Groenewold IT Solutions in Leer/East Frisia: a joint process workshop, a tightly scoped pilot with a few vendors, then extensions for additional tax and edge cases. Operational logic such as queues, retries, and notifications was part of the architecture from day one.
Results
Less typing, faster cycle times
Most invoices flow through without manual double entry; finance focuses on true exceptions and approvals. Cash-discount deadlines are met more reliably because documents are posted promptly and traceably.
Reference for hybrid automation
The project shows how n8n and UiPath complement each other: n8n connects cloud, AI, and communication, UiPath operates systems without an interface. In mid-sized companies with grown IT landscapes, this bridge is often the real value contribution.
Features
Feature overview
- Email intake and attachment detection via n8n (IMAP trigger)
- OCR and AI-assisted extraction of invoice fields
- Validation of IBAN, VAT IDs, and duplicates
- Approval workflow via Slack / Microsoft Teams
- Automatic ERP posting via UiPath in the desktop screen
- Filing of the original PDF in document management
- Queues, retry logic, and an audit-ready log
- Delivery by Groenewold IT Solutions (Made in Germany)
Project Details
Project
Wholesale & shared-service centreCompleted
Design, pilot and rollout (reference project)
Technologies
More References
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