ARQTA ARQTASELF-BILLING

Register the prior self-billing agreement

Guide for the supplier. It takes about 3 minutes and is done only once, in your own Portal das Finanças account.

Details you will need

The final form asks you for these two values only.

Why is it needed?

Under self-billing (autofaturação, art. 36.º do CIVA), the buyer company issues the invoice in your name. For the Portuguese Tax Authority (AT) to allow it, the supplier has to register the prior agreement (acordo prévio), authorising the buyer (adquirente). In the Portal’s own words:

“Esta operação autoriza o Adquirente a comunicar as séries de autofaturação com acordo prévio em seu nome.” (This operation authorises the buyer to report the self-billing series with prior agreement in your name.)

Without this registration, AT refuses the invoices, and no invoice can be issued. You do not need to create sub-users or share any credentials with us.

Step by step

1

Sign in to the Portal das Finanças

Sign in with your company’s credentials (the supplier’s) and open the series area:

Open the series area ↗
2

Choose “Comunicação de Séries de autofaturação com acordo” (reporting self-billing series with agreement)

The Operador Económico (economic operator) screen shows three cards. Click COMUNICAÇÃO DE SÉRIES (report series) on the middle card, the “com acordo” (with agreement) one.

Careful: do not use the “sem acordo” (without agreement) card on the right. It is meant for specific sectors (waste, cork, wood, electricity for self-consumption).
Operador Económico screen with three cards; the middle one, 'Comunicação de Séries de autofaturação com acordo', is highlighted.
The middle card is the right one.
3

Under “Autofaturação com acordo prévio” (self-billing with prior agreement), click REGISTAR (register)

Scroll down to the Autofaturação com acordo prévio section (at the bottom of the page) and click the REGISTAR button under Registar Acordo (register agreement).

Do not confuse it with Registar Série (register series) in the section above: that operation is done by the buyer, not by you.
'Acordo prévio de Autofaturação' page; in the 'Autofaturação com acordo prévio' section, the REGISTAR button is highlighted.
“Autofaturação com acordo prévio” section → REGISTAR.
4

Fill in and confirm

  • NIF do Adquirente (buyer’s NIF) - the company’s NIF: (given in the invitation e-mail)
  • Data de início de Autorização (authorisation start date) - in the format aaaa-MM-dd (year-month-day), e.g. 2026-07-01
  • Autorizações (authorisations) - the option “Autorizo o adquirente a comunicar séries em meu nome” (I authorise the buyer to report series in my name) is already ticked

Click CONFIRMAR (confirm).

'Registar acordo prévio de autofaturação' form with the fields NIF do Adquirente and Data de início de Autorização.
Only two fields: the buyer’s NIF and the start date.
5

Done

✓The agreement is registered immediately; there is no need to tell us.
✓The system used by the company detects the agreement automatically and registers the series with AT.
✓From then on, invoices are issued as normal.

You can check it at any time under Autofaturação com acordo prévio → Consultar Acordo (view agreement).

Have you registered the agreement?

Click so that we can confirm it with AT. If the agreement is active, the series are registered at once and invoicing is unblocked. You do not need to tell anyone.

Frequently asked questions

Do I have to create a sub-user?
No. Sub-users (sub-utilizadores) are created only by the buyer. The supplier only has to register the agreement.

Do I have to share passwords with the company?
Never. You register the agreement yourself, in your own account, and no credentials are shared.

Can my accountant do this?
Yes, as long as they access the Portal das Finanças on behalf of your company. Forward this page to them.

Can I end the agreement later?
Yes, under Autofaturação com acordo prévio → Finalizar Acordo (end agreement). From that date we can no longer issue invoices in your name.