What are Certificados de Aforro and how does Série F work?

What are Certificados de Aforro?

Certificados de Aforro (savings certificates) are a savings product issued by the Portuguese State and managed by the IGCP, the State's treasury and debt management agency². In plain terms: you lend money to the State and, in return, you earn interest. The capital is guaranteed (it is not exposed to stock-market swings), and you can start small, from €10 (10 units).

They have been one of Portugal's most popular ways to save for decades, especially for people who want safety and don't want to risk their capital. They differ from a term deposit in one important way: the interest compounds, and there is a premium that grows the longer you hold.

How does Série F of the savings certificates work?

Certificates are issued in series, each with its own rules. The series currently on sale is Série F¹. Its essential features are:

• Minimum subscription: 10 units (€10); each unit is worth €1.
• Maximum term: 15 years.
• Compounding: quarterly. Interest is added to your savings at the end of each quarter and itself starts to earn.
• Capital guaranteed by the State.
• Redemption possible from the third month after subscribing.

The big difference from a plain savings account is the interest-on-interest effect: by compounding, the certificates work much like compound interest, where time works in the saver's favour.

How is the interest rate calculated?

The Série F return has two components that add together¹:

Gross annual rate = base rate + permanence premium

The base rate is set every month and tracks the 3-month Euribor average (E3), rounded to three decimal places. It is capped at 2.5% and floored at 0%. So when market rates rise, the base rate rises (up to the 2.5% ceiling); when they fall, it falls. For reference, in May 2026 the base rate was 2.195%.

This is why there is no single fixed "savings certificate rate": the rate in your subscription month applies to the first quarter, and then it tracks the market quarter by quarter. In our savings certificates calculator you can enter the base rate for your subscription month and see an estimate, assuming that rate stays constant over the term.

Where to follow the monthly base rate

Because the base rate changes every month, it helps to know where to check it before subscribing or reviewing an existing holding. The IGCP publishes the base rate in force and the full Série F technical sheet on its official website¹. The rate in the month you subscribe sets the return for the first quarter; from then on, each quarter tracks the 3-month Euribor in force at the time.

In practice, this means there is no point trying to "time" the perfect moment: what matters is holding the investment long enough for the permanence premium to take effect. In our savings certificates calculator you can enter the current base rate and see an estimate of what it will earn over the term.

What is the permanence premium?

The permanence premium is the second component of the rate, and the real advantage for long-term savers. It is an amount that is added to the base rate and that grows with the years you hold the certificates¹:

Two details make a difference. First: the premium is not subject to the 2.5% cap on the base rate (it is added afterwards), so the total return can exceed that ceiling in the final years. Second: the premium rewards those who stay. Whoever redeems early gives up the higher premiums. It is not a penalty for leaving; it is a bonus for staying.

Are savings certificates taxed?

Like any product that earns interest, savings certificates are taxed. Interest is capital income (IRS Category E) and is taxed at a flat 28% withholding rate at source³. In practice, what compounds in the certificates is the interest net of tax.

This has a practical consequence: the advertised rate is always gross. To compare certificates with another product, such as a term deposit, look at the net value, after tax. That is exactly the figure the savings certificates calculator highlights as the main result.

Worked example

Imagine €10,000 subscribed at a base rate of 2.195% (May 2026), held for 10 years:

• In year 1 the rate is 2.195% (no premium).
• In year 10, the rate is already 3.195%: the 2.195% base plus the +1.00% premium.
• With quarterly compounding and the 28% tax, you finish with about €12,049 net.
• Net interest is roughly €2,049 after 10 years.

If the market base rate is different in the month you subscribe, the result changes, so it is worth testing your own scenario in the savings certificates calculator, which also shows the year-by-year growth and the moment each premium kicks in.

Savings certificates or term deposit?

There is no single answer. It depends on the term and the rates of the moment:

• Certificados de Aforro shine over the long term, thanks to quarterly compounding and the rising premium. They are ideal for money you won't need for several years.
• A term deposit tends to be simpler and more flexible short term, with a fixed rate known up front and short terms (6, 12, 24 months).

The honest way to decide is to compare the net value of both options for the same amount and term. Run a scenario in the term deposit calculator and the equivalent in the savings certificates calculator, and see which leaves more money in your pocket after tax.

Pros and cons of Certificados de Aforro

Like any product, savings certificates have strengths and limitations. It is worth weighing them before deciding.

For:

• Capital guaranteed by the State, one of the highest levels of safety available to a saver.
• Quarterly compounding and a rising premium, which reward long-term saving.
• Accessible: you can start from €10 and subscribe online through AforroNet.
• No subscription or maintenance fees.

Against:

• The base rate changes every month with Euribor and is capped at 2.5%; in periods of low rates, the return can be modest.
• The higher premiums only arrive after several years: redeeming early wastes the product's biggest advantage.
• Like any low-risk saving, in some years they may earn below inflation, eroding real purchasing power.
• The maximum limit per holder restricts anyone wanting to invest very large amounts.

On balance, they are a solid base for the safe, long-term part of your savings, provided the money really can sit untouched for several years.

How to subscribe and redeem

You subscribe at the CTT (post offices), on the IGCP's AforroNet portal or app, with a saver number linked to your NIF². Redemption is possible from the third month and the capital, being the State's, is always guaranteed. Just remember that leaving early means leaving the later years' premiums behind. With this product, patience is literally rewarded.