September 2026 marks the start of a new fiscal cycle in Portugal after the summer period, bringing a comprehensive set of deadlines for businesses, self-employed workers, and individuals. The Tax and Customs Authority establishes declarative and payment obligations related to IRS, IRC, VAT, Stamp Duty, contributions, and other taxes.
Regarding declarative obligations, the Monthly Salary Statement must be submitted by the 10th, Model Declaration 11 by the 15th, and various VAT declarations by the 21st. By the 7th, the information on invoices issued in the previous month must be communicated. Also by the end of the month, Model Declarations 30 for income to non-resident taxpayers, Model Declarations 62 and 63 for the Global Minimum Tax Regime, and VAT refund requests related to the previous calendar year must be submitted.
Regarding payment obligations, monthly and quarterly VAT must be paid by the 25th. By the 21st, the second installment payment on account of IRS for category B income, the delivery of withheld IRS and IRC, the delivery of Stamp Duty, and the audiovisual contribution must be made. By the end of the month, the second installment payment on account of IRC is due, the second additional installment payment on account of the state surcharge for entities with taxable profit exceeding 1,500,000 euros, the AIMI payment for holders of urban residential properties or land for construction, and the IUC payment for vehicles whose registration anniversary falls in September.
All declarations must be submitted via electronic data transmission through the Tax Portal, available for citizens, businesses, public entities, and certified accountants. The indicated source is the Tax Portal.
