Diogo opened his activity and sees everyone talking about “certified invoicing software”. He’s unsure: does he have to buy a program, or can he keep issuing receipts on the Portal das Finanças, for free? Good news: the Portal das Finanças is a free option provided by the AT. What changes with turnover is the obligation to issue via a certified program or the Portal - and there’s one number that marks that line.
The rule: always certified, not always bought
Two different things people mix up:
- Certification: any program you use to invoice must be AT-certified (since 2020) - a hand-made Word or Excel isn’t a certified program.
- Buying software: that’s optional. The Portal das Finanças lets you invoice for free and is the AT’s official alternative to a certified program - it works even once you’re required to issue through a lawful channel. You buy software when you need more automation, not because you have to leave the Portal.
What a certified program does (and the Portal too)
Certified software guarantees, by design, what the AT requires:
- sequential, continuous invoice numbering;
- ATCUD and, on certified-software documents, a QR code;
- integrity once issued - an invoice isn’t deleted or rewritten; you correct it with a proper document (a credit note);
- means to communicate the documents to the AT.
That communication has a deadline: the invoice data is communicated to the AT by day 5 of the following month. On the Portal it goes out automatically; with a certified program, check how and when the data is sent - responsibility for the deadline is always yours.
Portal or program?
- Free and official (the AT's app)
- Works even above €50,000
- Basic: one receipt at a time
- Buying it is optional (the Portal is the free alternative)
- Automates series, retainers, recurring clients
- Must be on the AT's certified list
Careful: if you buy a program, confirm it’s on the AT’s certified-software list - using a non-certified one is an offence. And there’s a related obligation (the SAF-T file) with its own rules depending on your regime; if you have organized accounting, check with your accountant what you have to send and when.
✅ In summary
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Any invoicing software must be certified (since 2020): a hand-made Word/Excel won’t do. Using a program is what depends - up to €50,000 turnover (in the prior year; annualised in the first year), you aren’t even required to use a program: the Portal das Finanças is enough and free.
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Above €50,000 in the prior year (or with organized accounting) you become required to issue via a certified program or the AT’s Portal das Finanças application (free); paid software is optional. Invoices are communicated to the AT by day 5 of the following month - make sure it’s done.
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FIZ is certified invoicing software - you issue with ATCUD, QR and communication automated (responsibility for the deadline stays yours), and automate what the Portal doesn’t. See the plans.
