Free · WordPress plugin
Install the plugin from the WordPress.org directory, put one shortcode on a page, and your visitors read e-invoices right on your website. The invoice is read in the visitor’s browser and never reaches your server.
In three steps
In the WordPress admin, search for “eInvoice Viewer” under Plugins, install and activate it.
Put the shortcode spev_einvoice_viewer in square brackets on any page. With bt=”1″ the BT numbers start visible.
Under Settings → E-Invoice Viewer you set the maximum file size, the default for the BT numbers and the design kit.
Requirements: WordPress 5.8 or later (tested up to 7.1) and PHP 8.2 or later. Licence: GPL 2.0 or later. What the Viewer shows and reads is described on the Viewer overview page. Without WordPress the same viewer is available as an app.
For developers
One shortcode is enough. Put spev_einvoice_viewer in square brackets on any page. With the attribute bt=”1″ the business-term labels start visible, with bt=”0″ hidden — and the visitor can toggle them at any time. The EN 16931 knowledge lives in a JavaScript core of its own that runs in the browser. The WordPress side is down to two PHP classes – shortcode and settings screen, about 41 KB. No PDF writer, no template engine, no framework, no vendor/. The viewer is a web component, <einvoice-viewer> – the same element in the shortcode, the stand-alone app and an embed in a foreign CMS. The invoice model it has read is available as viewer.model, alongside rawXml and syntax; the events einvoice-model-ready, einvoice-language-changed and einvoice-reset can be heard on the document. The model shape is fixed as a versioned JSON Schema, and the PHP and JavaScript paths produce the same shape – measured on every build.
Install a companion add-on and its capability appears directly in the same result view – same toolbar, no re-reading of the file: Technical Details (cardinality, data type, XPath, Field and Rule Browser), Visualizer (four print layouts and “Download as PDF”), Exporter (EN 16931 field-catalogue spreadsheet), Extended Profiles (ZUGFeRD/Factur-X EXTENDED, XRechnung Extension, EXTENDED-CTC-FR), Identifier Check (VAT ID, LEI, IBAN, national company numbers) and Inbound Check (the plausibility questions of an accounts-payable desk). With eInvoice Validator for KoSIT installed, a “Validate with KoSIT” button runs your own KoSIT validator against the invoice on screen; with eInvoice Validation Explorer for KoSIT the report is shown in plain language with BT/BG labels. Install, and the button is there – nothing needs configuring.
Free, no account and no outside service.