Certified invoicing in your product. FIZ reports every invoice to AT.
FIZ issues the invoices your app requests through the API, in each customer’s name, and returns the number and the PDF.
For SaaS, marketplaces, booking platforms and business management software. Each customer has a FIZ account and authorises your app.
Test app without a paid plan
- Guest
- Joana Lopes
- Stay
- 2 nights, double room
- Invoiced by
- Casa do Largo, Lda
- Total
- 180.00 €
- Invoice
- FT FIZ2026/57
How FIZ issues invoices from your app
Every sale in Portugal needs a certified invoice. FIZ issues it on behalf of each client through your app, so your product does not need its own AT certification.
FIZ connects the app to each customer
FIZ shows the owner the permissions the app asks for. The owner confirms with “Allow” and goes back to the app.
FIZ issues the invoice in the customer’s name
The app sends the buyer’s details, the items and the amounts through the API and asks for the invoice. FIZ sends back the invoice number and the PDF.
FIZ reports the invoice to AT
FIZ does this when the invoice is issued, as software certified by AT (No. 3041). The invoices also stay in the customer’s FIZ account.
Each invoice is issued in the seller’s name, with their NIF
Your app connects to each customer with a FIZ profile, self-employed or company. On a marketplace, each seller with their own NIF is one of these customers.
A new customer creates their FIZ account from your app, with an email and a NIF, and sets up the AT connection now or later. Then they go back to the app.
What if the AT connection comes later?
Until then, the app can already connect to the customer and create drafts. To issue, the customer’s profile needs the AT connection, automatic invoice reporting switched on and an invoice series for this year; the app sees through the API what is missing.
- Casa do Largo, LdaCompanyReady to issue
- Marta RibeiroSelf-employedReady to issue
- Loja Ponte, LdaCompanyDrafts only: no AT connection
One connection per profile, authorised by the owner
What your app does through the API
The app creates customer records, items and drafts. When it asks, FIZ issues invoices, simplified invoices, faturas‑recibo and credit notes for the full amount, records payments with a receipt and cancels documents.
The owner grants the permissions once, and FIZ issues each document the app asks for, with no further confirmation. The app sees only the records it created itself, unless it asks for access to all invoicing data.
What data does the app use?
The profile’s name, NIF, CAE and series, the invoices, the customer records and the items. The app has no access to transport documents, scheduled invoices, templates, pro formas or bank transactions.
Customer access: paid by the customers or by your platform
The only difference is who pays for access to FIZ: the AT connection, the permissions and the issuing are the same in both cases.
What is included when the platform pays?
Access through the API and the issuing of documents through your app. FIZ’s other paid features, such as the declarations or the PDF without the FIZ logo, depend on each customer’s plan.
Each customer pays for their own FIZ plan
If the customer has no paid plan yet, FIZ shows them the plans when they connect your app.
Plans that include the APIYour platform pays for its customers’ access
Customers need no paid plan of their own. We agree the terms with you, and when customers connect the app, they see that the platform pays for their access.
Where your brand appears and where FIZ appears
The customer sees FIZ when creating the account, during the AT connection and when authorising your app. If the customer has a paid plan, the invoice PDF comes without the FIZ logo.
Day to day, the customer invoices without leaving your app.
- In your app
- Name and domainInterfaceBilling for your product
- Outside your app
- Customer’s accountAT connectionManaging the connection
The owner disconnects the app at any time on the Integrations page in FIZ. The account and the issued documents stay in FIZ.
- Reservas MarAuthorised by Rui Marçal
- Agenda NorteAuthorised by Rui Marçal
Start with a test app
The test app connects without a paid plan to your profile and those of up to 20 people you list. Every invoice issued in a test is real; on a company profile, issuing works during the free trial or with a paid plan. Customers connect to a production app approved by FIZ.
Frequently asked questions about FIZ for platforms
Does the customer need a FIZ account?
Yes. Sign-up from your app takes the customer straight to creating the profile, without choosing a plan. The profile is for the activity the customer already runs, self-employed or as a company: creating it does not open a new business.
Who can authorise the connection?
The owner of the profile in FIZ: the self-employed person or the company’s owner. Each authorisation connects one profile to the app; for another profile, the owner authorises again.
Which FIZ plans include the API?
Every paid plan: Auto, Prime, Auto Pro and Prime Pro for the self-employed, and FIZ Pro and FIZ Max for companies. The customer pays FIZ for the plan and also gets that plan’s other features.
How do I test the integration before opening it to customers?
With the test app (Development): list the testers by email, even before they have a FIZ account. Each of them connects a profile they own.
The Node.js example on GitHub connects a profile and creates a customer record, an item and a draft invoice.
What is needed to connect the first customers?
A production app, registered separately, with public HTTPS URLs and a privacy policy. Submit it for review on the Integrations page in FIZ; once it is approved, your customers can connect it.
If you change settings that were already approved, the app goes back to draft and is unavailable to customers until FIZ approves it again.
When is an API key used, and when is OAuth used?
An API key connects the systems of whoever creates it to FIZ, such as their own website or CRM. OAuth connects your app to each customer, with the owner’s authorisation.
Can a customer use several apps and FIZ itself?
Yes. Each app has its own connection and its own records, and the customer keeps using FIZ with whatever plan they have.
On a marketplace, who invoices the platform’s commissions?
Your company, in its own name. If your company’s FIZ profile is also connected to the app, FIZ issues those invoices. Sales are still invoiced in each seller’s name.
How do I talk to FIZ about my platform?
Tell us by email what your platform does and how many customers you expect to connect. We agree the rest with you, including who pays for the access.