ON Time: Tax Calendar – May 2026

In business, things rarely happen in a straight line. Most of the time, several things are happening at once, with different levels of urgency and attention.

Between quick decisions and tasks that keep piling up, it’s easy to go into autopilot. But this month calls for the opposite: to slow down a little, understand what’s working, and identify what needs adjusting before moving forward. Sometimes, the smallest details make the biggest difference in day-to-day operations.

To help you keep track, we’ve gathered the main May deadlines in one place, in a straightforward way. That way, you know exactly what’s ahead during the month and what you shouldn’t miss.

May brings several important deadlines, and having this overview in advance helps you manage everything with more confidence and fewer surprises along the way.

Until 5 May

• Income Tax / Corporate Tax (IRS) /Corporate Tax (IRC) / VAT: Submission, by electronic transmission of data, of the details of invoices issued in the previous month, or confirmation of their absence, by individuals or companies with a registered office, permanent establishment or tax residence in Portugal and carrying out VAT-taxable operations.

Until 11 May

• Income Tax / Corporate Tax (IRS): Submission of the Monthly Remuneration Statement, by electronic transmission of data, by entities paying employment income subject to IRS, including exempt income or income excluded from taxation, under Articles 2, 2-A and 12 of the Personal Income Tax Code, reporting income, tax withheld, and deductions relating to mandatory social security contributions and union fees for the previous month.

Until 15 May

• Income Tax / Corporate Tax (IRS) / IMT / Stamp Duty: Submission of Model 11 Declaration, by electronic transmission of data, by notaries and other officials or entities performing notarial functions, as well as entities or professionals authorised to certify private documents relating to taxable income or property transactions, reporting acts carried out in the previous month.

Until 20 May

• VAT: Submission of the periodic VAT return, including applicable annexes, by monthly regime taxpayers, relating to operations carried out in March.
• VAT: Submission of the periodic VAT return, including applicable annexes, by quarterly regime taxpayers, relating to operations carried out in the 1st quarter.
• VAT: Submission via the Tax Authority portal of the classification of invoices and confirmation of the provisional return provided by the Tax Authority, based on available data, by retailers under the special taxation regime under Article 60 of the VAT Code, for the 1st quarter.
• VAT: Submission of the Recapitulative Statement, by electronic transmission of data, by monthly VAT taxpayers who carried out intra-Community supplies of goods and/or services in the previous month, and by quarterly taxpayers when the threshold of €50,000 is exceeded.
• Stamp Duty: Submission of the Monthly Stamp Duty Return (DMIS), by electronic transmission of data, by taxpayers carrying out taxable acts, contracts or documents subject to Stamp Duty, even if exempt, in the previous month.

Until 31 May

• VAT: Submission, by electronic transmission of data, of VAT refund requests for tax incurred in another EU Member State or in Portugal by non-EU taxpayers, when the refund amount exceeds €400 and relates to a period of at least three consecutive months, under Decree-Law no. 186/2009 of 12 August.
• Income Tax / Corporate Tax (IRS): Submission of Model 22 tax return by entities subject to Corporate Income Tax (IRC), whose tax period matches the calendar year.
• Corporate Tax (IRC): Submission of Model 22 tax return by entities subject to Corporate Income Tax (IRC), whose tax period matches the calendar year.

Until 1 June

• AIMI: Submission by married or cohabiting taxpayers of the option for joint taxation for the Additional Municipal Property Tax (AIMI), as provided in Article 135-D of the Property Tax Code, if not submitted in the previous year.
• AIMI: Submission by married taxpayers under joint ownership regimes who opt out of joint taxation, declaring property ownership allocation between spouses and joint assets, for individual AIMI assessment.
• Income Tax / Corporate Tax (IRS): Submission of Model 18 by entities issuing meal vouchers and other fringe benefit instruments.
• Corporate Tax (IRC): Submission of Model 54 by any entity resident or with a permanent establishment in Portugal that is part of a group required to submit country-by-country financial and tax reporting.
• Contribuições CESE: Submission of Model 27 relating to the Extraordinary Energy Sector Contribution (CESE), as per Article 7 of the relevant regime.

The interpretation presented here does not aim to standardise the interpretation or application of tax and accounting rules, is not binding on Moloni, and specialised professional advice should be sought for each of the matters addressed.