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 Thursday. 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 nine days 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 but has no tax number separate from its NIPC. After it is filed, you can invoice. Not before.

The statutory deadline is 15 days from the date the inscrição is completed and the Anuncio n.1 (the legal publication) appears on publicacoes.mj.pt. In practice the CC watches for the anuncio and counts from there. My NIPC arrived 15 May; the anuncio was published the same day; abertura was filed 29 May. Friday evening, last day of the window.

The form sets four things that have consequences for years:

1. IRC regime
2. VAT regime
3. CAE codes (your registered activity codes)
4. Plenos Poderes Declarativos (whether your CC can file declarations on your behalf)

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, or anything else, using your company's Portal das Finanças password. CCs have their own portal. They log in with their own professional credentials, and once a CC is associated with your company's tax file, they can act for it from there. 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 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: losses carry forward five years, there is no minimum tax on zero revenue, and the three-year lock-in risk of regime simplificado was not worth taking. 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. There is no separate application. There is no confirmation notice. 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 das Atividades Económicas (economic activity classification), the Portuguese equivalent of NACE. Every company picks a primary CAE and can add secondary ones. The codes matter for the IRC simplificado regime (they determine which coefficient applies), for invoicing, and for certain sectoral grants and incentives.

For Descodify, the relevant options were:

62010: Computer programming activities. The primary code for software development.

62020: Computer consultancy activities. Covers advisory and consulting around IT.

62090: Other information technology and computer services. The catch-all.

58290: Publishing of other software. Relevant if you sell packaged software products.

I registered 62010 as primary. The CC also added 62090 as secondary, which gives flexibility if invoicing anything adjacent to pure development.

The practical consequence for most founders: if you are on IRC regime simplificado with code 62010 or other activities listed in the Art. 151 CIRS profession list, you would fall under coefficient 0.75 in the simplificado formula, meaning 75% of revenue is taxable. If your activity falls under the residual "other services" category (roughly 0.10 coefficient), the tax is dramatically lower. This is the unresolved SaaS coefficient question from Part 1, and it is decided, in practice, by what CAE codes you put on the form.

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 with turnover below €15,000.00 per year. Under it, you charge no VAT and file no quarterly declarations. Simple, and tempting when you expect low early revenue.

I skipped it for two reasons.

The first is timing. The exemption ends the moment you cross €18,750 in a rolling year (the 25% tolerance band introduced by DL 35/2025). When it ends, you flip to normal VAT immediately: the invoice that crosses the threshold 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 pay for foreign software subscriptions (AWS, Vercel, Stripe fees, where reverse-charge VAT applies too), 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.

Normal quarterly VAT it was. The quarterly return is due by the 20th of the second month after each quarter ends. So Q1 (January to March) is filed by May 20.

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 files Modelo 22, IES and the quarterly VAT returns himself, through the CC portal, and you never hand over a senha. Off, he cannot, and then the only way anything gets filed electronically is with your credentials, 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", and no in-between where he drafts and I click approve. 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 (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 filing under his own credentials, so every future deadline needs your password or your own submission. 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 CAE + REI/VIES field

The form also asked about REI/VIES, the Registo de Operadores Intracomunitários (intra-EU VAT register). This toggles on your status as an intra-community operator, required if you invoice EU business clients or buy from EU businesses.

My CC enabled it. Correct call: a software company with European infrastructure providers and potential EU business clients should have REI/VIES from day one. Without it, you are not visible in the EU VIES database when clients check your VAT number.

What was declared

The final filing, comprovativo number 9996006301525:

• IRC regime: Geral
• VAT: Normal Trimestral
• CAE principal: 62010
• REI/VIES: 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. It helps AT estimate your VAT burden for the year. If you end up above or below it, you do not amend the abertura. The actual VAT flows through your quarterly 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 three-year consequences 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, REI/VIES 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) has a 30-day deadline from company formation. For a single-sócio Unipessoal Lda, it is a 10-minute online form at rcbe.justica.gov.pt. Easy to forget. €1,000 to €50,000 fine for missing it.

Segurança Social. Registration as sócio-gerente has to happen within 10 working days of the declared activity start (not from formation, but from the data de inicio de atividade on the abertura, which in my case was 2026-06-01). The specifics of the SS registration and the €537/month minimum base question are what Part 4 covers.

Invoicing. From 2026-06-01, the company can invoice under its NIPC. Any invoice issued before the abertura date with the company NIPC would be illegal. The company was not yet a sujeito passivo.

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.