I almost missed an August tax deadline in Portugal because, honestly, the month looks empty. June’s IVA slides into September, the big calendar pages are blank — and I was starting to believe the rumor that August “doesn’t count for anything.”
Then I sat down at the kitchen table with the Portuguese tax calendar spread out and printed it like a checklist. Turns out three real deadlines land on August 31 for independent workers. Not knowing which is which is the difference between closing the month calm and starting September paying interest charges (juros de mora) and small fines (contraordenações) for missed filings.
Here’s the honest version: August is only half a slow month. The VAT work is genuinely delayed, but invoice reporting and — in many cases — your income tax payment are right on time, ending on August 31. So let’s separate what stays in August from what moves to September.
Deadline 1: Report your invoices by August 31
If you bill through a certified invoicing program instead of through the Portal das Finanças, you’re required to report the details of your invoices — or confirm that there were none. Normally the cutoff is the 5th of the following month.
In August, that deadline is officially extended to August 31, covering July’s invoices. And here’s the trap that catches people: the rule applies even if you billed nothing in July. No invoices is itself something you have to declare, or you face a fine.
Deadline 2: Pay any assessed income tax (IRS) by August 31
If you filed your income tax return — Modelo 3 with Anexo B for independent work income — and received a tax assessment note (liquidação) from the tax office by July 31, you have until August 31 to pay the tax it shows, if there is any to pay. That rule lives in Article 97 of the IRS Code.
In practice, that same August 31 deadline is also when tax refunds from the AT are usually processed. So if money is coming back to you, it’s worth keeping an eye on your account through the end of the month.
Deadline 3: July’s social security contributions by August 31
The normal due date for independent workers’ social security contributions is the 20th of the following month. But for July’s contributions, Segurança Social has confirmed an exception: you can pay all the way until the last day of August — even if it’s not a business day — with no interest and no late fees.
If you have direct debit set up, you don’t need to do anything. You’re still responsible, though, for making sure there’s enough money in the account on the day it runs.
Why there’s no IVA deadline in August
Unlike invoice reporting and IRS, the VAT obligations that would normally fall in August — the monthly return for June and the quarterly return for the second quarter (April through June) — move to September. The declaration is due by September 21 and the payment by September 25, under Article 41 of the IVA Code.
If you’re on the quarterly regime, you only file the second-quarter return and pay in September. There is genuinely nothing VAT-related to do in August.
The August checklist
- Invoice reporting (e-fatura/SAF-T for July): by August 31
- IRS — payment of assessed tax: by August 31, if the assessment note was issued by July 31
- IVA (June monthly and Q2 quarterly): declaration by September 21, payment by September 25
- Social Security — July contributions: normal due date is the 20th; the extension to August 31 is reported consistently across sector sources, though it wasn’t confirmed directly from an official source in this check
August isn’t a fiscally empty month after all for people working for themselves. Knowing which obligations stay and which leave is the difference between closing the month calm and starting September paying interest charges.
One honest note: I’m a budgeter, not a tax advisor. The rules above are general information — your own situation might be different, so run the specifics past your accountant before you file.
One thing you can do today: pull up the official declaration calendar on Portal das Finanças and the payment calendar and mark all three dates on yours. Add the Segurança Social payment page to your bookmarks while you’re at it. Thirty seconds now saves you an interest charge in September.