Three solutions, one toolbox
Read invoices. Understand validation reports.
All three run as a WordPress plugin on your own site, process the file in memory and store nothing. The core is free; the Viewer has four paid extensions.
Solution 1 · free
(e)Invoice Viewer for PEPPOL & EN16931
One shortcode turns your page into a complete e-invoice reader. It reads ZUGFeRD / Factur-X PDFs as well as CII and UBL / XRechnung XML — credit notes included — and lays out all 164 business terms and 32 business groups. Empty fields stay visible, so you can see what the standard provides for and what this particular invoice left out. BT labels can be shown or hidden on the spot, and the tooltips come in three languages.
Four extensions for the Viewer
Solution 2 · free
(e)Invoice Validation Explainer for PEPPOL & EN16931
A KoSIT validation report gives you rule identifiers and XPath expressions. The Explainer turns that into something readable: it maps every finding to its EN 16931 term, explains the rule violation in plain language and puts the actual field value from the document next to it — along with the full document text, findings highlighted. It reads the report as XML and as HTML, and deliberately does not validate anything itself.
Solution 3 · free
eInvoice Validator for PEPPOL & EN16931
One shortcode puts the official KoSIT validator on your page — the very tool the XRechnung ecosystem relies on, run locally, with no third-party validation API. It checks against XRechnung 3.0.2, ZUGFeRD / Factur-X EN16931 including EXTENDED, and PEPPOL BIS Billing 3.0. The report is offered as an XML download — and appears in plain language as soon as the Explainer is active alongside it.
Requires a local Java runtime and a KoSIT validator installation; neither is bundled.
Three plugins, one upload
Nothing convinces faster than your own file.
Both demos run on the very plugins you would install on your own site — and store nothing.