ON Time: Tax Calendar - March 2026

Do you run a business and still aren’t quite sure what to expect when it comes to tax obligations? Don’t worry, you’re not alone! March is the ideal month to take a few minutes, get everything organised, set your priorities straight and avoid surprises that could complicate your day-to-day.

If you have a small or medium-sized business, this month really deserves your attention. Have you taken a moment to think about what went well over the past few months and what could have gone better? This is also a great time to anticipate what’s coming next and prepare your business for the challenges ahead.

You can take a deep breath — you don’t need to be an accounting genius! To help you out, we’ve put together the key tax dates for March in a clear and straightforward way, so you can stay on top of everything without getting lost and keep your business fully compliant.

Until 2 March

• IRS: Submission of Declaration Model 37, by electronic data transmission, by credit institutions, housing cooperatives, insurance companies, fund management companies and other complementary schemes referred to in Articles 16 and 21 of the Tax Benefits Statute.
• IRS: Submission of Declaration Model 39, by electronic data transmission, by debtor entities or entities that have paid or made available to the respective beneficiaries the income referred to in Article 71 of the CIRS, or any income subject to withholding tax at a definitive rate, in the previous year, where the beneficiaries are resident and do not benefit from an exemption or reduced rate.
• IRS: Submission of Declaration Model 45, by electronic data transmission, by entities providing healthcare services provided for in paragraphs 2 and 3 of Article 78-C of the CIRS, where such entities are not required to issue invoices or, although exempt, have not issued them.
• IRS: Submission of Declaration Model 46, by electronic data transmission, by entities providing education and training services provided for in paragraphs 5 and 6 of Article 78-D of the CIRS, where such entities are not required to issue invoices or, although exempt, have not issued them.
• IRS: Submission of Declaration Model 47, by electronic data transmission, by entities receiving amounts relating to expenses with care homes provided for in paragraphs 3 and 4 of Article 84 of the CIRS, where such entities are not required to issue invoices or, although exempt, have not issued them.
• IRS: End of the deadline for consultation and updating, by electronic transmission, of data relating to household composition and other relevant personal elements.
• IRS: Communication of attendance at educational establishments of dependants with income.
• IRS: Allocation of expenses and properties to the taxpayer’s activity under Category B, in accordance with Article 31(15)(a) and (b) of the CIRS.
• IRS: Communication of household members attending educational establishments located in inland territory or the autonomous regions, and the total amount of the respective expenses incurred.
• IRS: Communication, by electronic data transmission, of the duration or termination of long-term lease agreements benefiting from the reduced tax rate provided for in paragraphs 3, 4 and 5 of Article 72 of the IRS Code.
• IRS: Registration of invoices or other documents relating to leases resulting in the transfer of permanent residence to an inland territory.
• IUC: Payment of the Single Circulation Tax for February 2026.
• CIT / IRS: Submission of Declaration Model 10, relating to the previous year, by taxpayers who are debtors of income that was not declared in the Monthly Remuneration Declaration.
• IRS: Deadline for confirmation and communication, by purchasers of goods and services, of invoices on the E-fatura platform.
• IT / IRS: Submission of Declaration Model 25, by electronic data transmission, by entities benefiting from tax-relevant donations under the regime established in the Tax Benefits Statute and the Scientific Patronage Statute, received in the previous year.
• CIT / IRS: Submission of Declaration Model 30 relating to income paid or made available to non-resident taxpayers in December of the previous year.
• CIT / IRS: Submission of Declaration Model 42, by entities that pay non-reimbursable subsidies or grants within the scope of an activity covered by Article 3 of the CIRS, or to CIT taxpayers, relating to income granted in the previous year.
• IRS: Submission of Declaration Model 44, by electronic data transmission or on paper, by IRS taxpayers with Category F income who are exempt and have not opted for issuing electronic rent receipts, as well as the entities referred to in Article 78-E(7) of the CIRS.

Until 05 March

• IRS / CIT / VAT: Communication, by electronic data transmission, of the elements of invoices issued in the previous month by individuals or legal persons with registered office, permanent establishment or tax domicile in Portuguese territory and who carry out VAT-taxable transactions therein.

Until 10 March

• IRS: Submission of the AT Monthly Remuneration Declaration, by electronic data transmission, by entities owing employment income, for communication of income and respective tax withholdings, deductions made for mandatory contributions to social protection schemes and statutory health subsystems, and trade union dues, relating to the previous month.
• SS: Submission of the Monthly Remuneration Declaration to Social Security, by electronic data transmission, by entities owing employment income, for communication of income and respective deductions for mandatory contributions to social protection schemes, relating to the previous month.

Until 15 March

• VAT: Deadline to opt for the VAT payment method on imports of goods through the monthly periodic return on the Finance Portal, to take effect from the following month.
• Intrastat: Submission of the Intrastat Declaration by taxable persons whose annual transaction amounts exceed the assimilation threshold defined annually by Statistics Portugal (INE), relating to transactions in the previous month.

Until 16 March

• IRS / IMT / Stamp Duty: Submission of Declaration Model 11, by electronic data transmission, by notaries and other officials or entities performing notarial functions, as well as entities or professionals competent to authenticate private documents evidencing acts or contracts subject to income or wealth tax, relating to acts carried out in the previous month.
• IRS: Deadline for the Tax Authority to make available information on IRS deductions on the Finance Portal.

Until 20 March

• SS: Self-employed workers – Payment of Social Security contributions.
• VAT: Submission of the Periodic VAT Return, by electronic data transmission, together with any applicable annexes, by taxable persons under the normal monthly regime, relating to transactions carried out in January.
• Bank of Portugal: COPE – Communication of Operations and Positions with the Exterior relating to the previous month.
• Stamp Duty: Submission of the Monthly Stamp Duty Declaration and respective payment.
• IRS / CIT: Submission of the declaration and payment of IRS and CIT withheld at source on income paid or made available in the previous month.
• VAT: Submission of the Recapitulative Statement, by electronic data transmission, by taxable persons under the normal monthly regime who, in the previous month, carried out intra-Community supplies of goods and/or services to taxable persons registered in other Member States, where such transactions are located there under Article 6 of the CIVA, and by taxable persons under the normal quarterly regime where the total intra-Community supplies of goods to be included in the statement have exceeded €50,000 in the current quarter (or in any month of the quarter).

Until 25 March

• SS: Payment of Social Security contributions.
• VAT: Payment of VAT by taxable persons under the normal monthly regime, relating to transactions carried out in January.

Until 31 March

• VAT: Submission, by electronic data transmission, of the request for flat-rate compensation by taxable persons who have opted for the regime provided for in Articles 59-A to 59-E of the CIVA, relating to transactions covered by that regime and carried out in the previous year.
• IUC: Payment of the Single Circulation Tax for March 2026.
• AIMI: Submission, by an undivided inheritance through the head of the estate, of the declaration identifying all heirs and their respective shares, where it intends to exclude the equivalence of the inheritance to a legal person for purposes of the Additional Municipal Property Tax (AIMI), as provided for in Article 135-E of the Municipal Property Tax Code.
• CIT: Submission of the Declaration of Changes, by electronic data transmission, to opt for or waive the non-inclusion, for the purposes of determining taxable profit, of profits and losses attributable to a permanent establishment located outside Portuguese territory.
• CIT: Submission of the Declaration of Changes, by electronic data transmission, to opt for or waive, by the parent company, in relation to the group’s net financing expenses.
• CIT: Submission of the Declaration of Changes, by electronic data transmission, to opt for the Special Taxation Regime for Groups of Companies (RETGS), or to communicate the inclusion or exit of companies from the perimeter (except where the change results from cessation of activity), or the waiver or termination of application of the regime, where the tax period coincides with the calendar year.
• IRS / CIT / VAT: Submission of Declaration Model 38, by electronic data transmission, by credit institutions, financial companies and other entities providing payment services, relating to cross-border transfers and remittances of funds to entities located in a country, territory or region with a more favourable privileged tax regime, except those carried out by public law legal persons.
• CIT / IRS: Submission of Declaration Model 30 relating to income paid or made available to non-resident taxpayers in January.
• RS: Deadline to opt, through submission of the Declaration of Changes, for IRS taxpayers wishing to change between the simplified regime and the organised accounting regime.
• IRS: Deadline for submitting a complaint regarding the amount of IRS deductions by taxpayers.
• IRS: Submission of Declaration Model 13, by electronic data transmission, by credit institutions and financial companies involved in transactions with securities, standalone warrants and derivative financial instruments.
• CIT: Submission of the periodic income tax return Model 22, by electronic data transmission, by entities subject to Corporate Income Tax, whose tax period coincides with the calendar year.

The understanding expressed herein, not aiming at the standardisation of the interpretation and application of tax and accounting regulations, does not bind Moloni, and specialised advice should be sought for each of the matters addressed.