E-Rechnung für Shopify und WooCommerce: So wird jede B2B-Bestellung automatisch konform

Die E-Rechnungspflicht gilt nur für B2B (Geschäftskunden), nicht für B2C (Endverbraucher). Das klingt einfach — in der Praxis muss ein gemischter Shop aber zuverlässig zwischen beiden unterscheiden.

Lösungsvergleich

// shopify-webhook.js
const express = require('express')
const crypto = require('crypto')
const fetch = require('node-fetch')

const app = express()

app.post('/webhook/shopify/orders-paid', express.raw({ type: 'application/json' }), async (req, res) => {
  // HMAC-Validierung
  const hmac = req.headers['x-shopify-hmac-sha256']
  const hash = crypto.createHmac('sha256', process.env.SHOPIFY_WEBHOOK_SECRET)
    .update(req.body).digest('base64')
  if (hash !== hmac) return res.status(401).send('Unauthorized')

  const order = JSON.parse(req.body)

  // Nur B2B-Bestellungen (mit USt-ID) als E-Rechnung
  const vatId = order.billing_address?.company &&
    order.note_attributes?.find(a => a.name === 'vat_id')?.value
  if (!vatId) {
    console.log('B2C-Bestellung, keine E-Rechnung noetig:', order.name)
    return res.json({ received: true })
  }

  const lineItems = order.line_items.map((item, i) => {
    const netPrice = (item.price * (1 - (item.discount_allocations[0]?.amount || 0) / item.price / 100))
    return {
      invoiceLineIdentifier: String(i + 1),
      invoiceLineNetAmount: (netPrice * item.quantity).toFixed(2),
      itemName: item.name,
      invoicedQuantity: String(item.quantity),
      invoicedQuantityUnitOfMeasureCode: 'C62',
      itemNetPrice: netPrice.toFixed(2),
      invoiceLineVatInformation: { invoiceLineVatCategoryCode: 'S', invoiceLineVatRate: 19 }
    }
  })

  const netTotal = lineItems.reduce((s, l) => s + parseFloat(l.invoiceLineNetAmount), 0)

  const response = await fetch('https://api.rechnungsapi.de/api/v1/zugferd/createZugferdFromJson', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${process.env.RECHNUNGSAPI_TOKEN}`,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({
      invoice: {
        invoiceNumber: order.name.replace('#', 'INV-'),
        invoiceIssueDate: new Date().toISOString().split('T')[0],
        invoiceTypeCode: '380',
        invoiceCurrencyCode: 'EUR',
        seller: {
          sellerName: 'Ihr Shop GmbH',
          sellerVatIdentifier: 'DE123456789',
          sellerElectronicAddress: 'rechnungen@ihrshop.de',
          sellerPostalAddress: {
            sellerAddressLine1: 'Shopstrasse 1',
            sellerCity: 'Hamburg',
            sellerPostCode: '20095',
            sellerCountryCode: 'DE'
          }
        },
        buyer: {
          buyerName: order.billing_address.company || order.billing_address.name,
          buyerVatIdentifier: vatId,
          buyerElectronicAddress: order.email,
          buyerPostalAddress: {
            buyerAddressLine1: order.billing_address.address1,
            buyerCity: order.billing_address.city,
            buyerPostCode: order.billing_address.zip,
            buyerCountryCode: order.billing_address.country_code
          }
        },
        invoiceLine: lineItems,
        documentTotals: {
          sumOfInvoiceLineNetAmount: netTotal.toFixed(2),
          invoiceTotalAmountWithoutVat: netTotal.toFixed(2),
          invoiceTotalVatAmount: (netTotal * 0.19).toFixed(2),
          invoiceTotalAmountWithVat: (netTotal * 1.19).toFixed(2),
          amountDueForPayment: (netTotal * 1.19).toFixed(2)
        },
        vatBreakdown: [{
          vatCategoryTaxableAmount: netTotal.toFixed(2),
          vatCategoryTaxAmount: (netTotal * 0.19).toFixed(2),
          vatCategoryCode: 'S',
          vatCategoryRate: 19
        }]
      }
    })
  })

  const pdfBuffer = await response.buffer()
  // E-Mail versenden oder in Archiv speichern
  console.log('ZUGFeRD-Rechnung erzeugt fuer:', order.name)
  res.json({ received: true })
})

Den Webhook in Shopify einrichten: Admin → Einstellungen → Benachrichtigungen → Webhooks → "Bestellung bezahlt" → URL deines Servers eintragen.

Bei WooCommerce greifst du direkt auf den woocommerce_payment_complete Hook zu. Der Code läuft serverseitig in der functions.php deines Themes oder in einem Custom Plugin — kein separater Server nötig.

<?php
// functions.php - WooCommerce Hook nach Zahlung
add_action('woocommerce_payment_complete', 'generate_e_rechnung', 10, 1);

function generate_e_rechnung($order_id) {
    $order = wc_get_order($order_id);

    // Nur B2B (mit USt-ID)
    $vat_id = get_post_meta($order_id, '_billing_vat_id', true);
    if (empty($vat_id)) return;

    $line_items = [];
    foreach ($order->get_items() as $i => $item) {
        $net_price = $item->get_subtotal() / $item->get_quantity();
        $line_items[] = [
            'invoiceLineIdentifier' => (string)($i + 1),
            'invoiceLineNetAmount' => number_format($item->get_subtotal(), 2, '.', ''),
            'itemName' => $item->get_name(),
            'invoicedQuantity' => (string)$item->get_quantity(),
            'invoicedQuantityUnitOfMeasureCode' => 'C62',
            'itemNetPrice' => number_format($net_price, 2, '.', ''),
            'invoiceLineVatInformation' => [
                'invoiceLineVatCategoryCode' => 'S',
                'invoiceLineVatRate' => 19
            ]
        ];
    }

    $net_total = $order->get_subtotal();
    $payload = [
        'invoice' => [
            'invoiceNumber' => 'INV-' . $order->get_order_number(),
            'invoiceIssueDate' => date('Y-m-d'),
            'invoiceTypeCode' => '380',
            'invoiceCurrencyCode' => 'EUR',
            'seller' => [
                'sellerName' => get_bloginfo('name'),
                'sellerVatIdentifier' => get_option('woocommerce_vat_id'),
                'sellerElectronicAddress' => get_option('woocommerce_email'),
                'sellerPostalAddress' => [
                    'sellerAddressLine1' => get_option('woocommerce_store_address'),
                    'sellerCity' => get_option('woocommerce_store_city'),
                    'sellerPostCode' => get_option('woocommerce_store_postcode'),
                    'sellerCountryCode' => 'DE'
                ]
            ],
            'buyer' => [
                'buyerName' => $order->get_billing_company() ?: $order->get_formatted_billing_full_name(),
                'buyerVatIdentifier' => $vat_id,
                'buyerElectronicAddress' => $order->get_billing_email(),
                'buyerPostalAddress' => [
                    'buyerAddressLine1' => $order->get_billing_address_1(),
                    'buyerCity' => $order->get_billing_city(),
                    'buyerPostCode' => $order->get_billing_postcode(),
                    'buyerCountryCode' => $order->get_billing_country()
                ]
            ],
            'invoiceLine' => $line_items,
            'documentTotals' => [
                'sumOfInvoiceLineNetAmount' => number_format($net_total, 2, '.', ''),
                'invoiceTotalAmountWithoutVat' => number_format($net_total, 2, '.', ''),
                'invoiceTotalVatAmount' => number_format($net_total * 0.19, 2, '.', ''),
                'invoiceTotalAmountWithVat' => number_format($net_total * 1.19, 2, '.', ''),
                'amountDueForPayment' => number_format($net_total * 1.19, 2, '.', '')
            ],
            'vatBreakdown' => [[
                'vatCategoryTaxableAmount' => number_format($net_total, 2, '.', ''),
                'vatCategoryTaxAmount' => number_format($net_total * 0.19, 2, '.', ''),
                'vatCategoryCode' => 'S',
                'vatCategoryRate' => 19
            ]]
        ]
    ];

    $response = wp_remote_post('https://api.rechnungsapi.de/api/v1/zugferd/createZugferdFromJson', [
        'headers' => [
            'Authorization' => 'Bearer ' . get_option('rechnungsapi_token'),
            'Content-Type' => 'application/json'
        ],
        'body' => json_encode($payload),
        'timeout' => 30
    ]);

    if (!is_wp_error($response)) {
        $pdf = wp_remote_retrieve_body($response);
        $upload_dir = wp_upload_dir();
        file_put_contents($upload_dir['path'] . '/rechnung-' . $order_id . '.pdf', $pdf);
    }
}

Die USt-ID musst du im WooCommerce Checkout als Custom Field erfassen. Mit Germanized Pro oder dem WooCommerce EU VAT Plugin wird _billing_vat_id automatisch als Order Meta gespeichert.

Wer keinen eigenen Server betreiben möchte, kann n8n oder Make.com als Middleware einsetzen. Die Daten fließen dann per Webhook direkt vom Shop in das No-Code-Tool und von dort an rechnungsapi.de. Du willst dich nicht selbst darum kümmern? Wir richten den n8n-Workflow für dich ein — oder übernehmen die individuelle Implementierung komplett. Sprich uns einfach an.