The Income Tax delivery campaign began this Wednesday, April 1st, and runs until June 30th. During this period, the Tax Authority makes the provisional automatic IRS declaration and the result of the settlement available on the Finance Portal. If the elements are correct, the taxpayer can confirm them; If you do not do so and are covered, at the end of the period the provisional declaration becomes definitive.
One of the most repeated mistakes is assuming that the automatic IRS does not require verification. No dismissal. AT provides the data it has, but this does not replace a careful review of the declaration, the tax framework and the deductions reflected. Confirming without validating remains one of the most dangerous shortcuts in this campaign, according to .
In practice, the taxpayer may be accepting incomplete values, poorly reflected deductions or a tax framework that no longer corresponds to their reality. And when the error goes unnoticed, the expected refund may be lower than anticipated, or the tax payable may increase.
The error often starts before delivery
Most problems do not arise at the time the declaration is presented, but in the preceding months. In 2026, AT’s own Tax Agenda indicated March 2nd as the deadline for checking or communicating invoices and also for consulting and updating the composition of the household and other relevant personal elements. When these steps fail, the declaration arrives in April with holes that are difficult to correct.
This is where frequent cases come in, such as children who no longer appear correctly at home, changes in the family situation that were not communicated or expenses that remained unvalidated in the e-invoice. AT explains that properly communicating changes to the household makes it easier to confirm the automatic IRS and complete the income declaration.
In households with joint custody, the risk of error is even greater. According to the AT, if communication about alternating residence or the percentage of sharing of expenses is not made or is inconsistent between the two responsible parents, the Tax Authority considers that the dependent does not have an alternating residence and divides the remaining tax deductions into equal parts.
Forgotten invoices, attachments and income
Another common mistake is in deductions. Many taxpayers blindly trust what appears pre-filled, but AT itself reminds us that declaring or changing expenses and charges in Annex H or in the e-invoice requires proof. Translation: correction is possible in many cases, but you need to have documents that support this change.
There are also those who forget income obtained outside Portugal. For tax residents in national territory, this is a sensitive error, because the IRS is levied on all income, including that obtained outside Portuguese territory. The Finance Portal has its own area for income obtained abroad and refers to Annex J of the declaration. Leaving these amounts out can turn an expected refund into an issue with TA.
Among self-employed workers, the problem usually arises in Annex B. The nature of income, certain framing options and various fields linked to expenses and charges require attention. For those who mix independent activity with other sources of income, assuming that pre-filling solves everything on its own can change the final outcome of the settlement.
The detail that could cost you dearly in 2026
This year there is still an additional factor that requires attention: the Youth Income Tax. The day before the start of the campaign, Regulatory Decree No. 5-A/2026 was published, which updated the universe of taxpayers covered by the automatic income declaration, now including the income exemption for categories A and B provided for in the IRS Jovem regime. Anyone who is covered, or thinks they are covered, must confirm with special care whether the framework presented actually corresponds to their situation.
This means that the old habit of accepting and following can be costly to precisely those who hope to benefit most. In matters such as tax benefits, specific annexes or recent changes in rules, haste is rarely the taxpayer’s friend.
Ultimately, saying goodbye to a refund isn’t always the result of a big mistake. Often it only takes one ignored detail, a misclassified expense, a poorly communicated percentage or omitted income to change the final accounts.
Anyone who wants to avoid this scenario has a simple rule to follow until June 30th: review everything before sending. In Income Tax, trusting without confirming continues to be one of the most expensive mistakes for thousands of Portuguese people.
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