# Phase 08: Billing Engine + Invoice PDF

**Status:** Complete
**Completed:** 2026-03-16

## Goal

Automated monthly invoice generation, PDF export, mark-as-paid workflow, and overdue escalation.

## What was built

### Backend

**`billing/invoice_pdf.py`** (new service)
- `generate_invoice_pdf(invoice_id)` — renders Jinja2 HTML template → WeasyPrint PDF
- Stores at `/app/data/invoices/{invoice_id}.pdf`
- Sets `Invoice.pdf_path` in DB

**`templates/invoice.html`** (new Jinja2 template)
- Branded HTML invoice with school name, billing period, line items table, totals, payment instructions

**`routers/billing.py`** additions
- `GET /billing/invoices/{id}/pdf` — serve PDF (FileResponse), auto-generate if not yet created
- `POST /billing/invoices/{id}/mark-paid` — set paid_at, payment_method, payment_reference → status=paid
- Invoice list now includes `school_name` (joined)

**`tasks/billing.py`** fixes + additions
- Fixed missing `func` import in `generate_monthly_invoices`
- `check_overdue` enhanced:
  - 7-day overdue → send warning email to school billing contact
  - 30-day overdue → suspend school (set status = suspended)
- `generate_monthly_invoices` auto-queues `send_invoice_email_task` after creating each invoice

### Frontend

**`BillingPage.vue`** — full rewrite
- Invoice table with school name (not raw UUID), status badges, PDF download button
- Mark-as-paid modal: payment method dropdown + reference field
- Status filter + pagination
- "Generate Invoices" quick action (triggers Celery task)
- Overdue invoices highlighted in red

**`api.ts`** additions
- `downloadInvoicePdf(id)` — opens PDF in new tab
- `markInvoicePaid(id, data)` — PATCH to mark-paid endpoint
- `triggerGenerateInvoices()` — POST to trigger monthly invoice generation