Portugal stacks CIUS-PT XML, monthly SAF-T, QR and qualified e-signatures on every invoice.
Sandra runs a haberdashery off Rua da Prata in Lisbon. Six square metres. One till. Her certified accountant arrives the first Monday of every month with a USB stick. Every fifth, the SAF-T(PT) — the standard tax-audit XML Portugal demands — has to be filed at the Autoridade Tributária (AT, the tax authority). From 1 January 2026 her B2G invoices leave the till as CIUS-PT XML. From 1 January 2027 every PDF she emails to a wholesaler needs a qualified electronic signature.
01The pain
The fifth of the month. That is the day Sandra's certified accountant arrives with the USB stick, and the day last month's SAF-T(PT) billing file has to land at the Autoridade Tributária — in XML, from software the tax authority has personally certified. The European Commission's eInvoicing-Country page lists the legal anchors: Decreto-Lei 123/2018, Decreto-Lei 28/2019, the EN 16931 European standard, UBL 2.1 syntax, and CIUS-PT (the Portuguese Core Invoice Usage Specification) as the structured XML format mandatory for invoices to public buyers.1
Lisbon shopkeepers and Porto café owners take the second cliff more seriously than the first. Group Seres, the Iberian electronic-invoicing desk that tracks every postponement, dates the chain in detail: large enterprises caught first, the long tail of micro-firms promised "next year" each year. From 1 January 2027 a qualified electronic signature becomes mandatory on PDF invoices to businesses and consumers. A PDF without one stops being an electronic invoice; in the AT's reading, it becomes a typed-out paper invoice that happens to be a PDF — a different legal object, with different archival duties.2
EasyTax, Jornal Económico's digital-tax column for Portuguese accountants and small-business owners, calls 2026 the year the rest of the regime applies. The billing tool has to already sit on the AT-certified list. The CIUS-PT interface has to be live whether the shop sends one B2G invoice a year or none. Twelve months later, every business and consumer flow has to be re-platformed onto a tool that can attach a qualified signature to a PDF, not just print one.3,4
02Who solves this today
Portugal-active vendors that publicly self-market to the AT-certified billing / faturação eletrónica (electronic invoicing) / SAF-T(PT) / ATCUD / CIUS-PT niche on their own Portuguese-language homepages. Each entry verified live and self-marketed in the niche on the date of writing. The AT's own published list of certified software is the regulator's catalogue, referenced in section 01 — not a third-party solution. The list is intentionally narrow.
Listed providers publicly market to the Portuguese AT-certified / faturação eletrónica / SAF-T(PT) / ATCUD / CIUS-PT niche on their own homepages. Inclusion is not endorsement. Adjacent Portugal-active vendors were considered and excluded where their public homepage did not explicitly name the niche at the date of writing — Cegid (cegid.com/pt) returned HTTP 200 but the front page focused on general retail and HR management without surfacing AT-certification, faturação eletrónica, SAF-T(PT), ATCUD, CIUS-PT or the Primavera brand on the homepage proper, so it was dropped pending a re-check at the Cegid Primavera sub-site; Sage Portugal (sage.com/pt-pt) returned HTTP 403 on the date of writing and could not be verified against the named-niche-on-homepage rule, so it was dropped; Edicom (edicomgroup.com/pt) named SAF-T and faturação eletrónica B2B/B2G in passing but did not surface ATCUD or CIUS-PT on the homepage proper and was dropped per the named-niche-on-homepage rule; Tickelia, Storecove, Fonoa, Pikon and ecosio are positioned as enterprise / multi-jurisdiction tax-tech rather than Portuguese-PME-facing platforms and were dropped per the named-niche-on-homepage and SME-cohort rules. The Autoridade Tributária's own published list of certified software is the regulator's own catalogue and is referenced in section 01 as the regulator-published mechanic, not as a third-party solution provider.
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