Contesting a Tax Assessment from the Autoridade Tributária in Portugal in 2026 — A Practical Guide to the Reclamação Graciosa, the Recurso Hierárquico, Judicial Impugnação and CAAD Tax Arbitration

Sooner or later, many taxpayers in Portugal receive a bill from the tax office that they believe is simply wrong: an IMI property-tax note built on an inflated valuation, an IRS assessment that ignored a deduction, an IMT charge on a transaction that should have been exempt, or a VAT correction that misreads the facts. The good news is that a decision by the Autoridade Tributária e Aduaneira (Tax and Customs Authority, or AT) is not the last word. Portuguese law gives you a clear ladder of remedies — some free and paperwork-only, others fought in court or before an arbitration panel — to challenge it.

This guide walks through that ladder as it stands in 2026: what each step is, how long you have, what it costs, and how to stop the debt being enforced while you fight it. It is general information, not legal advice — for anything of real value, take professional help before a deadline passes.

Before anything: note the deadline on the notification

Almost every remedy runs from a date printed on the AT's notification (notificação) — usually the end of the prazo de pagamento voluntário (voluntary payment period). Miss the window and you generally lose that route, so the first thing to do with any assessment is diarise the deadline. Most challenges are filed online through the Portal das Finanças, either in the dedicated area for each remedy or through the e-balcão messaging channel.

Step one: the reclamação graciosa (free administrative complaint)

The reclamação graciosa (gracious complaint) is the standard first move. It is an administrative complaint filed with the AT itself, asking it to review and annul or correct its own act. You can raise the same grounds you could later argue in court, you do not need a lawyer, and it costs nothing.

• Deadline: 120 days, counted in most cases from the end of the voluntary payment period (the timing rules sit in article 102 of the CPPT, the Código de Procedimento e de Processo Tributário, or Code of Tax Procedure and Process).
• Decision time: the AT should decide within four months. If it stays silent past that, the law treats the silence as an indeferimento tácito (tacit rejection), which unlocks the next step.
• Cost: free.

Because it is cheap and low-risk, the reclamação graciosa is almost always worth trying first, even if you expect to escalate.

Step two: the recurso hierárquico (appeal up the chain)

If the reclamação is rejected — wholly or partly — you can lodge a recurso hierárquico (hierarchical appeal) to the official above the one who decided, ultimately the relevant director or member of government.

• Deadline: 30 days from notification of the reclamação decision.
• Decision time: the appeal should be decided within 60 days.
• Cost: free; no lawyer required.

The hierarchical appeal is optional — you can jump straight from a rejected reclamação to court or arbitration — but it is another free bite at the apple, and if it fails it does not close off the judicial routes: you keep 90 days from its (express or tacit) rejection to go to court.

Step three, option A: impugnação judicial (the tax court)

The impugnação judicial (judicial challenge) takes the dispute to a tribunal tributário (tax court). It is the traditional judicial route and can review essentially any illegality in the assessment.

• Deadline: three months from the relevant fact, or 90 days from the express or tacit rejection of a reclamação or hierarchical appeal.
• Cost: a taxa de justiça (court fee) scaled to the amount in dispute, plus, above the court's alçada (jurisdictional value threshold, €5,000 at first instance), mandatory representation by a lawyer.
• Speed: the slowest route — tax cases can run for years — but with a full appeal chain through the higher administrative courts.

Step three, option B: CAAD tax arbitration (faster, capped)

Since 2011, taxpayers have had an alternative to the courts: arbitration before the CAAD, the Centro de Arbitragem Administrativa (Administrative Arbitration Centre), under the RJAT (Regime Jurídico da Arbitragem Tributária, the Legal Regime for Tax Arbitration, Decree-Law 10/2011). The AT is bound to accept CAAD arbitration for claims up to €10 million under Portaria 112-A/2011.

• Deadline: 90 days, counted from the same facts as the judicial route (including the rejection of a reclamação or hierarchical appeal).
• Speed: the tribunal must generally decide within six months (extendable), far quicker than the courts.
• Cost: a taxa de arbitragem (arbitration fee) scaled to the value at stake — meaningful, but often recovered if you win.
• Finality: the decision binds the AT, with appeals only on narrow grounds (for example, to the Constitutional Court, or for conflicting case law). You cannot run both CAAD and a judicial impugnação against the same act — you choose one.

Arbitration has become popular precisely because it is fast and final; for a clean legal question on a mid-sized bill, many advisers prefer it to the courts.

The debt does not pause on its own

Challenging an assessment does not automatically stop the AT from collecting it. Once the payment deadline passes, the tax can go into execução fiscal (tax enforcement). To suspend enforcement while you contest, you normally have to provide a garantia idónea (an adequate guarantee — a bank guarantee, deposit, or mortgage) or, where paying or guaranteeing would cause serious hardship, ask for the guarantee to be waived. If you ultimately win and the guarantee proves to have been unnecessary, you can claim compensation for the cost of having provided it.

If you win: indemnity interest

Where the AT charged you tax that was not due, a successful challenge entitles you to juros indemnizatórios (indemnity interest) on the amount repaid, running from the payment. It will not make the process pleasant, but it does mean the State pays for its error.

A fallback when the deadlines have passed: revisão oficiosa

If you only realise there was an error after the reclamação window has closed, the revisão oficiosa (ex officio review) can be a longer-stop remedy — in cases of error attributable to the tax authority it can be requested within four years. It is narrower and more discretionary than a reclamação, but it has rescued many taxpayers who found the mistake late.

What This Means for Expats

• You have more than one chance: the free reclamação graciosa comes first, and losing it does not end the matter — the hierarchical appeal, the tax court and CAAD arbitration all remain open on fresh deadlines.
• Diarise every date: the remedies are strict on timing — 120 days, then 30, then 90. A missed deadline, not a weak argument, is what sinks most challenges.
• Match the route to the stakes: for a small, clear error, the free administrative complaint often does the job; for a larger, contested bill, CAAD arbitration is usually faster and more final than the courts, provided the claim is within the €10 million cap.
• Sort out the guarantee early: if the amount is large, decide before the payment deadline whether to provide a garantia to suspend enforcement — otherwise the AT can start collecting even while you are formally contesting.
• This sits alongside your other tax filings: the same logic applies whether the bill came from your Modelo 3 IRS return, an IMI property-tax note, or another head of tax covered in our overview of the Portuguese tax system.

Contesting the tax office is not only for big companies with law firms on retainer. The first rung of the ladder is free, filed online, and open to anyone — and for many wrongly issued bills, that is all it takes. For everything beyond it, the routes exist; the discipline that matters is watching the clock. And if the dispute is with another private party rather than the State, the Julgados de Paz small-claims courts follow a similarly accessible logic.