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Social Security quarterly declaration: 5 rules to submit it on time and without mistakes
Step Inside Accounting · Practical guide
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1. Know whether you have to submit it
The quarterly declaration is mandatory for self-employed workers who are already contributing, that is, after the first 12 months of activity. You have to submit it even if you invoiced nothing in the quarter: in that case, you declare zero.
As a rule, you do not have to submit it if you are exempt because you are also employed, within the income limits. If you have organised accounting, the base is the previous year’s profit and the rules are different: talk to us.
2. Note the four deadlines
The declaration is due by the last day of January, April, July and October. In each one you declare the previous three months:
| Submit by | Months declared | Contributions calculated from it |
|---|---|---|
| 31 January | October, November and December | January, February and March |
| 30 April | January, February and March | April, May and June |
| 31 July | April, May and June | July, August and September |
| 31 October | July, August and September | October, November and December |
In January, Social Security also asks you to confirm your income for the previous year.
3. Declare what you invoiced, month by month and without VAT
In the declaration you state, for each of the three months:
- the amount of services provided;
- the amount of sales of goods and of hotel and restaurant services, if you have any.
The amounts are without VAT. If you issued credit notes, deduct them. Social Security then applies 70% to services and 20% to sales – see how in our article on contributions. Use the list of invoices issued on the Portal das Finanças to check the figures: that is the data Social Security will cross-check later.
4. Submit it on Segurança Social Direta – and decide the base
The declaration is submitted online, on Segurança Social Direta, in the self-employed area. At the end, the system shows the relevant income and the resulting monthly contribution.
It is also the only moment when you can adjust the base by up to 25% up or down. If you do nothing, the calculated amount stands. Keep the submission receipt.
5. If you miss it or make a mistake, fix it quickly
Not submitting the declaration on time can lead to a fine. And mistakes come to light: every year, Social Security compares what you declared with the income you reported to the Tax Authority. If you declared less, you receive a notice with the missing contributions, which are already treated as overdue.
If you spot a mistake, talk to us straight away: it is easier to fix it in the same quarter than after the annual review.
Example
Ricardo is a consultant. Without VAT, he invoiced €2,000 in July, nothing in August and €3,000 in September 2026. By 31 October he submits the declaration with those three amounts:
- total for the quarter: €5,000;
- relevant income: €3,500 (70% of €5,000);
- monthly base: €1,166.67 (€3,500 ÷ 3);
- monthly contribution: €249.67 (21.4% of the base).
Ricardo pays €249.67 for each of the months of October, November and December, between the 10th and the 20th of the following month. For August he declares zero: as the base is the quarter’s average, the month without invoicing already lowers the contribution for the next three months.
Team tip
Put the 20th of January, April, July and October in your diary as a reminder – ten days before the deadline. If you send us the list of invoices for the quarter, we submit the declaration for you and tell you whether it is worth adjusting the base.
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This article is for information only and does not replace professional advice. Figures and rules are those in force at the date of publication and may change.
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