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Calculadora Capital

Savings Certificates Calculator

Certificados de Aforro are the Portuguese State savings product: capital-guaranteed, with interest that compounds every quarter and a premium that grows the longer you hold. Use the calculator to estimate how much Série F earns (after the 28% withholding tax) over the years.

The base rate is set every month (3-month Euribor, max 2.5%). Enter the rate for your subscription month, check the current value at IGCP. The permanence premium is added automatically by year.

Net value at maturity
€12,049.05
Net interest
€2,049.05
Gross value (before tax)€12,951.85
Tax paid−€902.80

Year-by-year growth

YearGross rateGross valueNet value
12.20%€10,221.31€10,158.98
22.45%€10,473.53€10,339.00
32.45%€10,731.96€10,522.21
42.45%€10,996.77€10,708.67
52.45%€11,268.12€10,898.44
62.70%€11,574.88€11,111.45
72.70%€11,889.99€11,328.64
82.70%€12,213.68€11,550.06
92.70%€12,546.18€11,775.81
103.20%€12,951.85€12,049.05

Educational estimate, not financial advice. Assumes a constant base rate; the real value varies with the monthly rates.

Video: how to use the calculator

What savings certificates are

They are a capital-guaranteed savings product issued by the Portuguese State (through the IGCP), with subscriptions from €10. The series currently on sale is Série F. Interest compounds (it is added to your savings and itself starts to earn) and the maximum term is 15 years.

How the interest rate is calculated

The return has two parts. The base rate is set every month and tracks the 3-month Euribor average (E3), capped at 2.5% and floored at 0%. On top of it comes a permanence premium that grows over time: +0.25% from year 2 to 5, +0.50% from year 6 to 9, +1.00% in years 10–11, +1.50% in years 12–13 and +1.75% in years 14–15. The premium is not subject to the 2.5% cap, so the total return can exceed it in the final years.

Quarterly compounding and the 28% tax

Interest is capitalised at the end of each quarter (annual rate ÷ 4), so the next quarter earns on a larger balance. As capital income, it is taxed at a flat 28% withholding rate at source; what compounds is the net interest. The calculator therefore highlights the net value (what you actually receive) and also shows the gross value for comparison.

Worked example

With €10,000 and a base rate of 2.195% a year (subscribed in May 2026), held for 10 years, you finish with about €12,049 net, roughly €2,049 of interest after tax. In year 10 the gross rate is 3.195% (the 2.195% base plus the 1% premium). If the base rate rises or falls the result changes, so you can enter the rate for the month you actually subscribe.

Frequently asked questions

What is the savings-certificate interest rate today?
The base rate is updated every month and tracks the 3-month Euribor, capped at 2.5%. In May 2026 it was 2.195%. Always check the current month on the IGCP website and enter it in the calculator; the permanence premium is then added on top depending on the years held.
Is the interest taxed?
Yes. Interest is capital income and is taxed at 28% (the flat withholding rate) at source. What compounds is the net interest, so the calculator shows the net value as the main result.
What is the permanence premium?
It is an add-on to the base rate that rises the longer you hold the certificates: it starts at +0.25% in year 2 and reaches +1.75% in years 14–15. It rewards long-term saving and is not subject to the 2.5% base-rate cap.
Can I withdraw the money whenever I want?
You can redeem from the third month after subscribing. Interest is paid by capitalisation and the capital is always guaranteed, but redeeming early means losing the permanence premiums of the later years.

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Author: Thorben Rasmus Idel · Reviewed by: Nahar Geva · Last reviewed: 2026-05-31