The submission of the IRS tax return remains, in 2026, one of the main tax obligations for taxpayers in Portugal, applicable to residents and, in certain situations, to non-residents with Portuguese-source income.
Proper compliance with IRS submission requirements is essential to avoid penalties, late-payment interest, corrections by the Portuguese Tax Authority (AT) and delays in refunds. Although the tax return model remains relatively stable, practice shows that doubts and frequent errors persist, especially in cases involving foreign income, family changes, or changes of residence.
At FA ACCOUNTING, we handle dozens of IRS tax return submissions every year and know that an incorrect return may result not only in additional tax, but also in administrative obstacles and loss of tax benefits. In this article, we explain who is required to file an IRS return in 2026, the applicable deadlines, the main annexes, and how to ensure a correct submission.
Who Must Submit an IRS Tax Return in 2026?
All taxpayers who earned taxable income in 2025 are required to submit an IRS tax return, namely:
- Employment or self-employment income;
- Pensions;
- Rental income (property income);
- Investment income;
- Capital gains (sale of property, shares, crypto-assets, etc.);
- Income obtained abroad, when applicable.
There are some situations in which taxpayers may be exempt from filing, but these are limited and depend on the type, amount, and source of income.
IRS Submission Deadline in 2026
In 2026, the IRS tax return for income earned in 2025 must be submitted:
From 1 April to 30 June 2026
This deadline is the same for all taxpayers, regardless of the type of income earned.
Late submission may result in:
- Fines;
- Loss of tax benefits;
- Delays or suspension of refunds.
Submission Model: IRS Form 3
The IRS tax return is submitted using Form 3, to which the relevant annexes for each type of income must be attached.
The most common annexes include:
- Annex A – Employment income and pensions;
- Annex B or C – Self-employment income;
- Annex F – Rental income;
- Annex G – Capital gains;
- Annex H – Tax benefits and deductions;
- Annex J – Income obtained abroad.
Correct selection and completion of the annexes is crucial for the accurate calculation of tax payable.
Automatic IRS in 2026
The Automatic IRS option remains available in 2026 for taxpayers with straightforward tax situations, namely:
- Only employment income or pensions;
- No foreign income;
- No complex capital gains;
- No need for additional annexes.
Although it is a useful tool, it is not suitable for every situation and should be used with caution, as it may not reflect all deductions or the taxpayer’s specific circumstances.
Situations Requiring Special Attention When Submitting the IRS
Foreign Income
Foreign income must be declared in the IRS return, even if it has already been taxed abroad. It is essential to correctly apply double taxation treaties to avoid being taxed twice.
Real Estate Capital Gains
The sale of property may result in significant tax liabilities, especially when there is incorrect application of:
- Reinvestment rules;
- Legal exemptions;
- Adjustments of values and deductible expenses.
Self-Employment Income
Requires increased attention regarding:
- Simplified regime or organised accounting;
- Withholding tax obligations;
- Declaration of all invoiced income.
Changes in Household Composition
Marriages, divorces, births or deaths may affect:
- Applicable tax rates;
- Deductions;
- The chosen taxation model.
Most Common IRS Filing Errors in 2026
- Omission of income;
- Incorrect declaration of capital gains;
- Improper use of Automatic IRS;
- Failure to declare foreign income;
- Outdated household information;
- Failure to validate expenses on the e-Fatura platform.
These errors may lead to:
- Additional tax assessments;
- Fines and interest;
- Official corrections by the Tax Authority.
Impact of Correct IRS Submission
A correctly completed tax return allows for:
- Accurate calculation of the tax due;
- Prompt receipt of tax refunds;
- Avoidance of audits and penalties;
- Access to legally available deductions and tax benefits.
An incorrect submission may result in paying more tax than legally due or facing tax regularisation procedures.
How to Ensure Correct IRS Submission in 2026
- Early organisation of documentation
- Timely validation of expenses on e-Fatura
- Careful review of income and annexes
- Verification of applicable deductions and benefits
- Professional support in more complex situations
How Can FA ACCOUNTING Help?
At FA ACCOUNTING, we provide comprehensive support throughout the IRS submission process:
- Individual analysis of each tax situation;
- Correct completion and submission of the tax return;
- Verification of deductions and tax benefits;
- Support with foreign income and capital gains;
- Legal tax burden minimisation.
We work with a preventive approach, ensuring tax compliance and peace of mind for our clients.
Prepare Your IRS Submission Safely in 2026
Contact us and avoid errors, fines, or loss of tax benefits on your IRS tax return.
Note
This article is for informational purposes only and is based on legislation in force in 2026. It does not replace personalised tax advice, especially in situations involving complex or international income.
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