Custom Invoice Approval App — Microsoft Graph API + LLM Extraction, Local Hosting

**Custom Invoice Approval Application — Microsoft Graph API + LLM Extraction** I'm looking for an experienced full-stack developer to build a custom invoice approval and payment recommendation application for a client in construction project management. This is a fully scoped, fixed-price build, and I have a detailed specification ready to share with shortlisted candidates. This is Phase 1 of a phased engagement. For the right developer, there is further work to follow — additional phases on this project, plus ongoing builds across other clients. **How I work** I handle the client relationship and all client-facing work. You focus purely on technical execution — clear scope, fixed price, clean deliverables. This is an execution-focused role, not a client-facing or partnership one. **Critical constraint — please read before applying** This must be built as a custom application running entirely on the client's own infrastructure. No third-party cloud data storage. No reliance on hosted n8n cloud, Make, or Zapier for the core workflow. The client's data cannot leave their servers under any circumstances. If your approach depends on hosted automation platforms, this isn't the right fit. **What the application does** - Triggers on invoice attachments arriving in individual Microsoft Outlook inboxes via Microsoft Graph API (no shared mailbox) - Extracts invoice data across varying consultant formats using an LLM (Claude or OpenAI) — invoice number, consultant, amount, GST, project, date - Verifies extracted amounts against an Excel fee proposal - Sends an approval notification via Microsoft Teams — Approve / Query / Reject, with a notes field - On approval, auto-generates a professionally formatted PDF payment recommendation - Updates an Excel budget register (append only — never overwrites existing data) - Maintains a full, searchable, exportable audit trail - Web-based, mobile responsive, multi-user **You must have** - Strong custom application development background (not no-code or platform-only) - Direct experience with the Microsoft Graph API (Outlook + Teams) - LLM-based document extraction experience - Comparable builds you can walk me through **To apply, please tell me** 1. How you'd architect this as a custom app on the client's own infrastructure 2. Your approach to PDF data extraction across variable invoice formats 3. How you'd implement the Teams approval layer (bot vs webhook) 4. A comparable build you've delivered — with a link or walkthrough 5. Your fixed price and realistic timeline Fixed price only. I'm looking for someone reliable who delivers clean, scoped work — and who I can keep working with long term across future projects.