Bootstrapping a Startup in Portugal: The Form That Locks In Your Tax Structure

This is Part 3 of Bootstrapping a Startup in Portugal, a first-person account of forming and running a Unipessoal Lda as a foreign founder. Part 1 was the IRC tax structure decision before formation. Part 2 covered why I formed the Lda, the overhead, and the salary and benefits questions still open. This post is what happened on the day we actually registered activity at AT.

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The NIPC arrived on a Friday. Fifty-seven days after the first company-name submission. I had a legal entity.

What I did not have was any clarity on what happened next, or in what order, or what decisions I was actually making when the accountant (contabilista certificado, CC) filed the abertura de atividade on my behalf two weeks later.

I know this now because I asked. Not because anyone volunteered it.

What the form actually is

Abertura de atividade is a single declaration at AT that registers your company as a tax-paying entity. Until it is filed, the company exists legally and has its NIPC, but it is not registered for any activity and cannot invoice. After it is filed, you can invoice. Not before.

The statutory deadline is 15 days from the date the company is presented for registration at the commercial registry (CIRC Art. 118.º). My CC watched for the anúncio (the legal publication on publicacoes.mj.pt) and counted from there. My NIPC arrived 15 May; the anúncio was published the same day; abertura was filed 29 May, a Friday evening, which my CC treated as the last day of the window.

The form sets three things that have consequences for years:

1. IRC regime
2. VAT regime
3. CAE codes (your registered activity codes)

It also leaves a fourth thing in its starting state: Plenos Poderes Declarativos, which starts at NÃO and which only you can change later. More on that below.

None of these are explained to you. The form is filed and then it is done.

Who actually files this, and why nobody asked me first

Here is the thing nobody walked me through, and it nearly cost me a late-filing fine.

A contabilista certificado does not file your abertura de atividade using your company's Portal das Finanças password. CCs log in to the Portal das Finanças with their own professional credentials, and once a CC is associated with your company's tax file, they can act for it from there. For the abertura, your company's AT password never enters the picture.

For an Lda with organized accounting, opening activity is itself part of the CC nomination flow, which the CC runs through his own access. There was nothing for me to hand over.

That is not how it played out. There was confusion over whether the company senha was needed before anything could be filed, and we lost days to it. By the time my solicitor settled the question, we were on what my CC counted as the last day of the 15-day window, and the abertura went in at 9pm on a Friday. A few more days and I would have been filing late, with the fine that comes with it, over a credential that was never needed in the first place.

I am not telling this as a complaint about my CC. It is a pattern I have now seen twice. You go to an accountant and say "help me set up an activity", or in this case "help me open the Lda", and the choices just get made for you. No walkthrough, no "here are your options". When I first registered as a trabalhador independente years ago, the more common version happened: my accountant already had my Portal das Finanças password (I wrote about that here), so my activity was registered before I even knew there were decisions to make. Most of the time the defaults they pick are fine. But it is your name on the file, "fine by default" is not the same as "the right choice for you", and you only find that out if someone stops to ask.

The lasting fix is not "do not share the password". It is plenos poderes declarativos, the setting that lets the CC file under his own access for good. But that one waits until the engagement is in writing. More on it below.

The IRC question was already settled

Part 1 of this series covered the regime decision in detail. By the time abertura came around, I had already concluded that regime geral was the right call for a year-one software company expecting a loss: tax losses carry forward to later years, while regime simplificado taxes a share of revenue even in a year the company makes a loss. The CC agreed. That part was clean.

What I did not know until afterward was that the IRC regime decision happens inside the abertura form, as one field among many. You either flag regime simplificado or you do not, and if you do not, you are on regime geral by default. (You can still opt into simplificado in a later year with a declaração de alterações by the end of the second month of that year, so geral is not a permanent choice.) You find out which regime you are on by checking your AT enquadramento after the fact.

The CC filed without the simplificado flag. Regime geral, as intended.

The CAE codes I chose

CAE stands for Classificação Portuguesa de Atividades Económicas (economic activity classification), the Portuguese equivalent of NACE. Every company picks a primary CAE and can add secondary ones. The codes are your registered activity, the starting point for which IRC simplificado coefficient applies, and they matter for certain sectoral grants and incentives.

For Descodify, the relevant options sat in CAE division 62 (programming, IT consultancy and other IT services), plus software publishing for anyone selling packaged software products.

I registered computer programming as the primary code. The CC also added the "other IT services" code as secondary, which gives flexibility if invoicing anything adjacent to pure development.

The practical consequence for most founders: on IRC regime simplificado, an activity listed in the Art. 151 CIRS table (programmers are on it, as code 1332) takes coefficient 0.75, meaning 75% of revenue is taxable. If your activity falls under the residual "other services" category (coefficient 0.10), the tax is dramatically lower. This is the unresolved SaaS coefficient question from Part 1. AT looks at what the company actually does, not only at the code on file, so the CAE you pick is where the question starts, not where it is settled.

For us on regime geral it does not directly matter: the simplificado coefficients are irrelevant. But for anyone considering the simplificado, the CAE code choice is consequential in a way that nobody hands you a guide to.

The VAT decision

I registered for normal quarterly VAT from day one. No Art. 53 exemption.

The Art. 53 exemption applies to businesses whose national turnover in the previous year was not above €15,000.00 and that make no export operations; a business that is just starting uses its own estimate for the year, which is why mine qualified. Under it, you charge no VAT, and for purely domestic activity you file no periodic declarations. Simple, and tempting when you expect low early revenue.

I skipped it for two reasons.

The first is timing. Under the tolerance band introduced by DL 35/2025, if turnover in the year passes €18,750, you flip to normal VAT immediately: the invoice that crosses that line must already include VAT. Switching mid-year adds accounting friction and can surprise clients who have received VAT-free invoices from you.

The second is that the exemption only covers domestic outbound Portuguese activity. If you invoice EU business clients (reverse charge applies from the first invoice regardless of your Art. 53 status), or if you buy business services from a supplier established outside Portugal (where you self-assess the VAT under reverse charge), you have VAT obligations from day one anyway. Art. 53 does not shield you from cross-border VAT mechanics. Most software companies are already outside the exemption's practical scope by virtue of their client and supplier mix.

One thing I only understood later: choosing normal VAT while you qualify for Art. 53 is an opt-out, and it binds you to the normal regime for at least five years. It is not the reversible default it looks like on the form.

Normal quarterly VAT it was. The quarterly return is due by the 20th of the second month after the quarter ends, so Q1 (January to March) is filed by May 20, with one exception: the Q2 return is deferred to 20 September. That is my first one.

Plenos Poderes Declarativos

This one is buried in the form and rarely explained, and it connects directly to the credentials question above.

Plenos Poderes Declarativos is a single on/off toggle, and it controls one thing: whether your CC can file at AT using his own credentials, without your password. On, he submits Modelo 22, IES and the quarterly VAT returns himself, with his own credentials, and you never hand over a senha. Off, he still prepares and signs them, but each submission needs your password, which drops you straight back into the problem from the section above. It is all-or-nothing: there is no "he files the VAT return but I approve the annual IRC". On or off, for everything.

A few things I only understood afterward.

You grant it, not the CC. The toggle lives in your company's area of the Portal das Finanças (Serviços → Dados Cadastrais → Contribuinte → Confirmar Poderes). A CC cannot grant himself full powers, so when the abertura was filed the only state it could be in was off. Mine reads Plenos Poderes: NÃO on the comprovativo.

Off does not give you oversight. It gives you friction. I had assumed NÃO meant "every declaration waits for my approval", which sounded like the visibility I wanted. It does not. Visibility comes from the portal regardless: everything filed under your NIF is there to read, on or off. All NÃO does is stop the CC submitting under his own credentials, so every future deadline needs your password. It recreates the problem; it does not protect you.

So the destination is on, but not yet. Granting plenos poderes hands someone autonomous authority to file in your name, and I am not doing that on a handshake. Right now I have a verbal agreement with my CC and no signed contract. The order matters: formalize the engagement first (scope, fees, what he files, how I see it, where liability sits), then flip plenos poderes to SIM. And do it with margin: the first quarterly VAT return is coming, and if the contract is still unsigned and the toggle still off when it lands, you are scrambling over credentials on a deadline. That is the exact situation that nearly cost me a fine the first time.

The intra-EU field

The form also asked about intra-EU operations: the box for Prestação/Aquisição de Serviços Intracomunitários, which you tick before supplying services to, or buying services from, businesses in other EU countries.

My CC ticked it. Correct call: a software company with European infrastructure providers and potential EU business clients needs it from day one.

What was declared

The final filing, comprovativo number 9996006301525:

• IRC regime: Geral
• VAT: Normal Trimestral
• CAE principal: computer programming (division 62)
• Intra-EU services: enabled
• Plenos Poderes: NÃO
• Volume de negócios declared: €10,000 (estimated for the year)
• Activity start: 2026-06-01

The volume de negócios is a forecast, not a commitment. In the first year it is what sets whether you file VAT monthly or quarterly. The actual VAT flows through your periodic returns.

What I did not get, and should have asked for

No consultation before filing. No walkthrough of each field and what it locked in. The CC received my instruction (regime geral, normal VAT) and sent me the comprovativo afterward.

The filing was technically correct. The problem is not what was chosen (the choices were sensible) but that a form with consequences of up to five years was filed without a phone call to walk through it first.

The CC's professional obligation is to file correctly and on time. Knowledge transfer is not part of the service unless you negotiate it explicitly. So negotiate it.

What I would do differently: in the week before the 15-day deadline, send the CC a written list of the decisions with your own reasoning attached ("I want regime geral because X, quarterly VAT because Y, intra-EU services enabled because Z, and plenos poderes left off until our engagement is in writing"). Ask for written confirmation that this matches what is being filed, with the exact field values. This creates a shared record and forces the conversation before the form is submitted rather than after.

What changes now

The company has a tax identity. The clock on a few obligations starts:

RCBE. The Registo Central do Beneficiário Efetivo (beneficial owner registry, EU AML compliance) is due within 30 days of the company's registration. For a single-sócio Unipessoal Lda held personally, it is a short online form on the RCBE website. Easy to forget, and if it is not filed the company may not distribute profits, contract with the State or receive public funds. The RCBE has its own glossary entry.

Segurança Social. I was told I had 10 working days from the activity start on the abertura to register myself as sócio-gerente. That turned out not to be how it works: the registry notifies Segurança Social of the gerente's appointment and Segurança Social enrols you, and the company's own deadlines run from Segurança Social's requests and from the start, cessation or any change it has to report, never from the abertura. Part 4 covers the registration and the minimum-base question.

Invoicing. From 2026-06-01, the declared activity start, the company could invoice under its NIPC, through certified invoicing software.

This series, so far

Bootstrapping a Startup in Portugal:

• Part 1: Portugal SaaS Tax Regime - which IRC coefficient applies to a software company, and the unresolved SaaS classification question
• Part 2: Setting Up an Lda - why Lda over sole trader, regime geral, overhead, the salary and benefits decisions still open
• Part 3: this post - the abertura de atividade, CAE codes, VAT registration, and what the form actually decides

Registering a Company in Portugal (the formation saga):

• Part 1: Starting a Business in Portugal in 24 Hours
• Part 2: One Step Forward, Many Steps Sideways
• Part 3: Heard of SOLVIT?
• Part 5: The Path That Actually Worked

Part 4 of this series: Social Security registration as sócio-gerente, the €537 minimum base, and the acumulação rules that may or may not apply.