E-Invoice EN 16931 for OpenCart — ZUGFeRD / Factur-X, XRechnung and Peppol BIS (Slovakia, Belgium) from orders

E-Invoice EN 16931 for OpenCart turns orders into electronic invoices under the European standard EN 16931: ZUGFeRD / Factur-X (a PDF/A-3 with the XML inside), XRechnung 3.0 in the CII and UBL syntaxes, and Peppol BIS Billing 3.0 for the Slovak e-faktúra, mandatory between Slovak businesses from 1 January 2027. One module for OpenCart 4, 3 and 2.3; everything is generated in your shop — no external service, no subscription, no order data handed to third parties.

Running WooCommerce? There is a separate plugin for it — E-Invoice EN 16931 for WooCommerce: ZUGFeRD / Factur-X and XRechnung 3.0 from WooCommerce orders.

Honestly about testing. The module went through full runs in clean shops on OpenCart 4.1.0.3, 4.0.2.3 (pdo driver), 3.0.5.0 and 2.3.0.2 on PHP 7.0, installed with the stock installer, with real checkouts in the storefront: all 76 XRechnung files (CII and UBL, invoices and credit notes) ACCEPTABLE in the official KoSIT 1.6.3 validator with the XRechnung 3.0.2 configuration, all 76 PDF and CII files valid in Mustang 2.26 (EN 16931 and veraPDF PDF/A-3b), all 12 Peppol BIS files without errors against the UBL 2.1 schema, the CEN EN 16931 rules and OpenPeppol BIS 3.0.20. The total of every document equals the order total, also with a coupon and in a second currency. We have not tested real portals and providers yet — ZRE / OZG-RE, Chorus Pro, Peppol access points, a certified Slovak delivery service: try it on your own shop in the 7-day Pro trial. The tax content of the invoice is the seller’s settings, not tax advice.

What the customer sees

• Fields for business customers — VAT ID, buyer reference / Leitweg-ID and, for Slovakia, IČO and DIČ. They are ordinary OpenCart custom fields, created by the module with one button, so they work on the default checkout, in registration and in the account, and next to One Page Checkout.
• A check right at the field: a VAT ID with a wrong format, a Slovak DIČ or IČO of the wrong length stop the order with the message next to the field. With Pro and VIES switched on, a number that VIES reports as not registered is refused too; an unreachable VIES never blocks an order.
• The invoice by e-mail (Pro): the PDF with the XML inside, plus the XRechnung XML for orders with a Leitweg-ID and the Peppol XML for Slovak B2B.
• Invoices in the account (Pro): on the order page of the customer account there is an “Invoices” block with the PDF and XML. Links are keyed per document: another customer or a visitor gets nothing.

What the admin gets

• E-invoice panel on the order page: issue the invoice, preview the PDF, download the PDF, CII, XRechnung CII and UBL, Peppol BIS; see credit notes and correct the buyer data (VAT ID, buyer reference, IČO, DIČ).
• Pre-flight check against a real order: the module builds the document with your settings and tells you what is missing, without using an invoice number.
• VAT categories set automatically from the order: standard rate S, zero rate Z, reverse charge AE and intra-Community supply K for an EU business customer with a VAT ID, export G, services abroad and small business E — each with a reason text and VATEX code.
• Totals exactly as in the order: products, shipping and fees with their tax per rate, coupons as allowances per VAT group, vouchers and store credit as a prepaid amount, the second currency of the order.
• Gap-free numbering from a pattern like INV-{YYYY}-{N:5} under a lock, with yearly restart and a start number to continue from your previous tool; “Rebuild” re-creates a document under the same number.
• Register of documents with filters and every file.

Slovak e-faktúra: Peppol BIS and the delivery service

From 1 January 2027 a Slovak VAT payer issues invoices for domestic supplies to Slovak businesses in a structured form under EN 16931 and hands them to a certified delivery service (§ 85o and § 76a of Act 222/2004 on VAT, as amended by Act 385/2025). The module covers the shop’s part:

• for a Slovak seller and a Slovak business customer the invoice is issued also as Peppol BIS Billing 3.0 (UBL), with the DIČ of both sides as Peppol address 0245, groups 23 % / 5 % and the document in Slovak;
• a DIČ or IČO of the wrong length is refused at checkout;
• Pro sends the Peppol XML to your delivery service: by a button on the order page or automatically after the invoice is issued. The answer of the provider goes into the register and the order history; a failed hand-over is marked as failed and can be repeated.

Every provider has its own API. The module supports the common form — an HTTPS address that takes the UBL XML in the request body, with an API key in a header you name; the key is stored encrypted, plain http is refused, the provider’s certificate is verified. We tested it against our own HTTPS endpoint (key accepted, wrong key → HTTP 401 shown on the order), not yet against a real certified provider.

Belgium: Peppol BIS for B2B since 1 January 2026

Since 1 January 2026, Belgian VAT payers invoice each other only with structured electronic invoices — Peppol BIS Billing 3.0 over the Peppol network. The module covers the shop’s part:

• for a Belgian seller and a Belgian business customer the invoice is also issued as Peppol BIS Billing 3.0 (UBL): the enterprise number (KBO / BCE, 10 digits) of both parties is the Peppol address and the legal entity identifier under scheme 0208, taken from the company number field or derived from the BE VAT ID;
• the company number field at checkout checks the check digits (mod 97): a mistyped number is refused next to the field before the order is placed;
• 21 % and 6 % as separate VAT groups; the document in Dutch or French, by the language of the order;
• a Belgian consumer gets the usual PDF / Factur-X, no Peppol file;
• Pro sends the Peppol XML to your access point from the order page or automatically after the invoice is issued; the answer goes into the register and the order history.

We tested the hand-over against our own HTTPS test endpoint, not yet against a real Belgian access point. Every provider has its own API; the module supports the common form — an HTTPS address that takes the UBL XML, with an API key in a header. Every Peppol file was checked with the official OpenPeppol rules (PEPPOL-EN16931-UBL 3.0.21) and the CEN EN 16931 rules.

France: the e-invoicing reform 2026 / 2027

Since 1 September 2026 every French company must be able to receive e-invoices, and large and mid-sized companies (ETI) must also issue them; SMEs and micro-enterprises issue from 1 September 2027. Invoices between companies go through a platform approved by the tax administration (plateforme agréée), sales to consumers are e-reported. The module produces the Factur-X with the data of the reform, ready to upload to your platform:

• SIREN of the seller and the business customer (scheme 0002), SIRET as identifier (0009), electronic addresses under scheme 0225;
• category of the operation (BT-23): goods, services or both, separately for invoices already paid; the B2B / B2C note;
• the option for paying VAT on debits (services): BT-8 = 5 and the mandatory mention on every invoice;
• the mandatory notes PMD (late payment penalties), PMT (fixed recovery fee of €40) and AAB (early payment discount), with ready texts you can change;
• a SIREN / SIRET field at checkout: a number of the wrong length is refused next to the field. B2B or B2C is decided by the customer’s SIREN — from this field or from a French VAT ID;
• a pre-check against the French BR-FR rules shows what is missing; only the currency blocks the invoice (next point);
• French invoices are issued in euro only. For another currency rule BR-FR-CO-12 also wants the VAT total in euro — at the latest Banque de France rate (based on the ECB rate) known on the day the tax becomes chargeable (CGI, art. 266-1 bis). OpenCart’s rate is a different one (manual or taken at order time), so a true amount cannot be derived from it. The module therefore does not turn a French seller’s non-euro order into an invoice: the reason shows on the order page and, for automatic issuing, in the order history; no number is used. The module’s main screen warns when other currencies are enabled in the shop; credit notes for invoices already issued work as usual;
• Pro: a CSV for the e-reporting of consumer sales — totals per day, currency, kind of operation and VAT rate, to enter into the platform. The official e-reporting flow itself is produced by the platform.

Every French invoice was checked with the official Factur-X / EN 16931 rules (Mustang, veraPDF) and the French BR-FR schematron (FNFE-MPE, version 1.4.0.04). The module has no direct connection to a particular platform.

Pro: automation, credit notes, customer account and a ZIP for the accountant

• Automatic issuing when the order reaches the statuses you choose, with the e-mail to the customer.
• Credit notes (type 381): a full one when the order gets Refunded / Reversed, and a partial one for any amount from the order page, split over the invoice’s VAT rates and referencing the invoice; an amount above the invoice is refused.
• Invoices in the customer account with keyed links.
• Hand-over to the Slovak delivery service, by button or automatic.
• Hand-over of Belgian invoices to your Peppol access point, by button or automatic.
• CSV for the French e-reporting — consumer sales per day, currency, kind of operation and VAT rate.
• VIES check of the VAT ID at checkout, answers kept for a day.
• Your logo on the PDF and a ZIP for the accountant per period: PDF, XML and a CSV list.

How it works — step by step

1. Enter the seller details (name, address, VAT ID, tax number or register number, contact) and the payment details (IBAN, BIC, days until due).
2. Create the buyer fields with one button each: VAT ID, buyer reference / Leitweg-ID, IČO, DIČ, company number (SIREN / SIRET, Belgian enterprise number).
3. Run the pre-flight check on any order — the module shows whether the document will be valid and what to add.
4. A business customer places an order and enters the VAT ID (a public-sector buyer — the Leitweg-ID, a Slovak company — IČO and DIČ).
5. Click “Issue invoice” on the order page — or, with Pro, the invoice is issued by itself on the chosen status, e-mailed to the customer and, for Slovak B2B, handed to the delivery service.
6. A refund → a credit note; at month end — a ZIP for the accountant.

Under the hood

• Standards: EN 16931 (urn:cen.eu:en16931:2017), ZUGFeRD / Factur-X EN 16931 profile with XMP metadata and the embedded XML, XRechnung 3.0 in CII and UBL, Peppol BIS Billing 3.0 (CustomizationID urn:cen.eu:en16931:2017#compliant#urn:fdc:peppol.eu:2017:poacc:billing:3.0).
• PDF/A-3b with an sRGB profile and embedded fonts — German, French and Slovak diacritics print correctly.
• Totals by the EN 16931 rules: VAT per group base, the difference to OpenCart’s rounding closed with the rounding amount — the amount due equals the order total.
• Numbers under a lock: two orders in the same second never get the same number; the pre-flight check uses none.
• Small business without VAT ID: the tax number is written as seller identifier (BT-29), so BR-CO-26 is met.
• OpenCart events and own tables (cc_einvoice_document, cc_einvoice_order, cc_einvoice_kv) — no core file edits. Uninstalling keeps the register (documents have to be retained by law); “Delete data on uninstall” removes the tables and the fields the module created.

Installation

1. OpenCart 4: Extensions → Installer → upload cc_einvoice.ocmod.zip (do not rename the archive) and click “Install”. OpenCart 3: Extensions → Installer → cc_einvoice-oc3.ocmod.zip, then Modifications → Refresh. OpenCart 2.3: copy the contents of the upload/ folder of cc_einvoice-oc2.ocmod.zip to the shop root (FTP or the hosting file manager).
2. Extensions → Modules → E-Invoice EN 16931 → “Install”, then “Edit”.
3. Seller and payment details, number format; create the buyer fields.
4. Pre-flight check on an order, then “Issue invoice” on a test order.
5. For Pro: the “Licence” tab — the key from the e-mail after payment, or the 7-day trial; then the statuses for automatic issuing and, for Slovakia or Belgium, the address and key of the delivery service or the Peppol access point.
6. Updating from 1.0.0 on OpenCart 4: OpenCart takes a new version only after the old one is uninstalled, and the uninstall deletes the module’s settings. Write the settings down first (seller, payment, number formats, VAT, Pro), then: Modules → E-Invoice EN 16931 → Uninstall → Installer → delete the old archive → upload the new one → Install → Modules → Install, and enter the settings again. The module links the buyer fields of 1.0.0 (VAT ID, reference, IČO, DIČ) by itself — do not create new ones; once it shows what to enter again and the last invoice and credit note numbers. Documents, numbering, customer data and the licence stay. Invoice links in e-mails already sent stop working; the customer account shows new ones. From 1.1.0 the module keeps a copy of its settings and puts them back by itself. On OpenCart 3.x and 2.3 the new archive simply goes over the old one and the settings stay.