Most tax calendars give you the rule and leave you to work out the date. The rule says day 20; the date is sometimes the 21st, the 22nd or the 27th, because deadlines move off weekends. Below are the actual 2026 dates with those adjustments already applied.
The recurring ones
| Obligation | When |
|---|---|
| Communicate invoices to e-fatura | Day 5 of the following month |
| Validate the previous year's invoices for IRS deductions | 2 March |
| Social Security quarterly declaration | Last day of Jan, Apr, Jul, Oct |
| Social Security contribution payment | Between the 10th and the 20th of the following month |
| IRS annual return (Modelo 3) | 30 June |
Quarterly IVA in 2026
| Period | File | Pay |
|---|---|---|
| Q4 2025 | 20 February | 25 February |
| Q1 2026 | 20 May | 25 May |
| Q2 2026 | 21 September | 25 September |
| Q3 2026 | 20 November | 25 November |
Q2 is the one worth reading twice — it is filed in September rather than August, and two separate rules stack to produce that date.
Monthly IVA in 2026
| Period | File | Pay |
|---|---|---|
| November 2025 | 20 January | 26 January |
| December 2025 | 20 February | 25 February |
| January | 20 March | 25 March |
| February | 20 April | 27 April |
| March | 20 May | 25 May |
| April | 22 June | 25 June |
| May | 20 July | 27 July |
| June | 21 September | 25 September |
| July | 21 September | 25 September |
| August | 20 October | 26 October |
| September | 20 November | 25 November |
| October | 21 December | 28 December |
Month by month
| Month | What is due |
|---|---|
| January | 20th monthly IVA (Nov) · 26th pay · 31st SS declaration |
| February | 20th quarterly IVA (Q4 2025) and monthly (Dec) · 25th pay both |
| March | 2nd e-fatura validation · 20th monthly IVA (Jan) · 25th pay |
| April | 20th monthly IVA (Feb) · 27th pay · 30th SS declaration |
| May | 20th quarterly IVA (Q1) and monthly (Mar) · 25th pay both |
| June | 22nd monthly IVA (Apr) · 25th pay · 30th IRS annual return |
| July | 20th monthly IVA (May) · 27th pay · 31st SS declaration |
| August | 5th e-fatura · 10th–20th SS contribution · no IVA filing |
| September | 21st quarterly IVA (Q2) and monthly (Jun and Jul) · 25th pay all |
| October | 20th monthly IVA (Aug) · 26th pay · 31st SS declaration |
| November | 20th quarterly IVA (Q3) and monthly (Sep) · 25th pay both |
| December | 21st monthly IVA (Oct) · 28th pay |
When is the IRS deadline in Portugal in 2026?
30 June for the annual Modelo 3 return.
When is quarterly IVA due in 2026?
Filing on 20 February, 20 May, 21 September and 20 November; payment on 25 February, 25 May, 25 September and 25 November.
Is there an IVA deadline in August 2026?
No. The June and July periods are both filed on 21 September, so August carries no IVA filing deadline and September carries two.
When must invoices be sent to e-fatura?
By day 5 of the month following the month they were issued. Validating the previous year's invoices for IRS deduction purposes is separate, and falls on 2 March.
When are Social Security declarations due?
The quarterly declaration is due by the last day of January, April, July and October. The contribution itself is paid between the 10th and the 20th of the month following the month it relates to.