Invoices API

Create, manage, and send invoices. Supports sales invoices, quotes, credit notes, and incoming invoices.

Invoice Types

Type	German	Description
rechnung	Ausgangsrechnung	Sales invoice
angebot	Angebot	Quote / proposal
gutschrift	Gutschrift	Credit note
eingangsrechnung	Eingangsrechnung	Purchase invoice

List Invoices

GET /api/invoices?type=rechnung&status=offen&page=1&limit=25

Param	Type	Description
type	string	Filter by invoice type
status	string	entwurf, offen, teilbezahlt, bezahlt, storniert
customerId	uuid	Filter by customer
from / to	date	Date range (ISO 8601)

Create Invoice

POST /api/invoices

{
  "type": "rechnung",
  "customerId": "customer-uuid",
  "items": [
    {
      "position": 1,
      "description": "Web Development - March 2026",
      "unit": "hours",
      "quantity": 40,
      "unitPrice": "95.00",
      "taxRate": "20.00"
    }
  ],
  "notes": "Payment within 14 days.",
  "paymentTermDays": 14
}

Send via Email

POST /api/invoices/:id/send

{
  "to": "[email protected]",
  "subject": "Invoice RG-2026-0042",
  "message": "Please find your invoice attached."
}

Download PDF

GET /api/invoices/:id/pdf

Record Payment

POST /api/invoices/:id/payments

{
  "amount": "1900.00",
  "date": "2026-03-22",
  "method": "bank_transfer"
}

E-Invoice Formats

GET /api/invoices/:id/ebinterface   # Austrian standard
GET /api/invoices/:id/zugferd       # EU standard

Statuses

Status	Description
entwurf	Draft
offen	Open — sent to customer
teilbezahlt	Partially paid
bezahlt	Fully paid
storniert	Cancelled

Get Invoice

GET /api/invoices/:id

Returns a single invoice with all items, customer, and payment data.

Update Invoice

PUT /api/invoices/:id

Same body as Create Invoice. Draft invoices can be fully updated. Sent invoices (offen) allow updating notes, footer text, and custom fields only.

Delete Invoice

DELETE /api/invoices/:id

Soft-deletes the invoice. Only invoices with status entwurf (draft) or storniert (cancelled) can be deleted. Returns 204 No Content.

Email Preview

Returns the resolved email subject and body (from your email templates, with all variables substituted) and the customer's email address — use this to pre-fill the send dialog before sending.

GET /api/invoices/:id/email-preview

Response:

{
  "to": "[email protected]",
  "subject": "Your quote AN-2026-0042",
  "body": "Dear Ms. Müller,\n\nPlease find your quote attached..."
}

Offer Detail Description (Markdown → PDF)

Quotes (angebot) support an optional detailed description in Markdown that is rendered as separate page(s) appended after the quote in the PDF.

Set or update the detail description:

PUT /api/invoices/:id
Content-Type: application/json

{
  "detailsMarkdown": "## Project Scope\\n\\n- Item one\\n- Item two"
}

Generate with AI:

POST /api/ai/offer-details

{
  "customerName": "Acme GmbH",
  "items": [
    { "description": "Backend Development", "quantity": 80, "unit": "Std" }
  ],
  "headerText": "Web platform relaunch",
  "instruction": "Focus on technical approach and timeline"
}

Response:

{
  "ok": true,
  "markdown": "## Project Overview\\n\\nThis proposal covers..."
}

Requires Pro or Business plan. The generated Markdown is returned for review — save it via PUT /api/invoices/:id with detailsMarkdown.

Item Ordering

Items are stored and rendered in the order of the position field (ascending). When updating an invoice, reorder items by changing their position values. The API always saves items in the submitted array order and renumbers positions 1..N automatically — so to reorder, simply submit the items array in the desired order.