Currencies and monetary unions

How to identify who issues a currency, which countries share a currency, and when a foreign currency is used unofficially

When you compare countries, the currency column in a fact sheet often lists a symbol and a name, but that single entry hides three distinct layers: the issuer (the institution that creates and regulates the money), the formal legal tender (what the government accepts for taxes and debts), and the de facto medium of exchange (what people actually use in shops). Getting these three straight is the difference between understanding a country’s monetary system and misreading it.

Use this three‑question decision rule every time you encounter a country’s currency:

1. Who issues it?, Look for the central bank or monetary authority named in the country’s constitution or law.
2. Is it shared?, Check whether the same currency name and code are used by more than one sovereign state.
3. Is a foreign currency used unofficially?, Ask whether a second currency circulates alongside or instead of the official one, especially in border regions, tourist economies, or high‑inflation environments.

Below, each layer is explained with current examples and source years so you can apply the rule to any country you research.

The issuer: central banks and monetary authorities

Every official currency has a single issuer, usually a central bank or a currency board. For example, the Bank of Japan (BOJ) issues the yen, the Reserve Bank of India (RBI) issues the rupee, and the Federal Reserve issues the US dollar. In monetary unions, the issuer is a shared central bank that acts for multiple countries. The European Central Bank (ECB) issues the euro for the about 20 eurozone members (2025, ECB). The Eastern Caribbean Central Bank (ECCB) issues the Eastern Caribbean dollar for eight island states (2025, ECCB). The Central Bank of West African States (BCEAO) issues the West African CFA franc for eight countries, and the Bank of Central African States (BEAC) issues the Central African CFA franc for six (2025, IMF).

When you see a currency, note the issuer, it tells you where monetary policy (interest rates, money supply, exchange rate decisions) is made. If the issuer is a foreign central bank, the country using that currency has no control over its own monetary policy.

Shared currencies: monetary unions

A monetary union exists when two or more sovereign states agree to use the same currency under a shared institutional framework. As of 2025, the IMF lists 20 countries that belong to formal monetary unions (excluding the eurozone itself). The largest by both population and GDP is the eurozone, about 350 million people and roughly €14 trillion in combined GDP (2025, ECB).

Other formal unions include:

• CFA franc zone: 14 African countries split into two groups, the West African Economic and Monetary Union (8 countries, BCEAO) and the Central African Economic and Monetary Community (6 countries, BEAC). Both currencies are pegged to the euro and guaranteed by the French Treasury (2025, IMF).
• Eastern Caribbean Currency Union: 8 countries and territories (Anguilla, Antigua and Barbuda, Dominica, Grenada, Montserrat, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines) using the Eastern Caribbean dollar, issued by the ECCB (2025, ECCB).
• CFP franc: 3 French overseas collectivities (French Polynesia, New Caledonia, Wallis and Futuna) using the CFP franc, pegged to the euro and issued by the Institut d’Émission d’Outre‑Mer (2025, IEOM).

A country can also adopt another country’s currency unilaterally without joining a formal union. Seven countries use the US dollar as sole legal tender: Ecuador, El Salvador, the Marshall Islands, Micronesia, Palau, Timor‑Leste, and Zimbabwe (2025, IMF). Two countries (Panama and Zimbabwe) use the dollar alongside their own local currency (2025, IMF). Similarly, three countries use the Australian dollar (Kiribati, Nauru, Tuvalu); four use the New Zealand dollar (Cook Islands, Niue, Pitcairn Islands, Tokelau); and three use the Indian rupee (Bhutan, India, Nepal), all as sole legal tender (2025, IMF).

The key distinction: a monetary union involves a multilateral treaty and a shared central bank; unilateral adoption involves a sovereign decision to use a foreign currency, with no say in its issuance.

Unofficial and de facto use

Official legal tender is not always what people use day‑to‑day. In several countries, a foreign currency circulates unofficially alongside or instead of the official one. The most common cases are:

• High inflation or hyperinflation: When the local currency loses value rapidly, residents switch to a stable foreign currency, typically the US dollar or the euro, for savings, large purchases, and sometimes everyday transactions. Zimbabwe, after its hyperinflation episode, now uses the US dollar alongside its own dollar (2025, IMF). In Lebanon, the Lebanese pound remains official, but dollars are widely used in real estate, education, and healthcare (2025, IMF).
• Tourism‑driven economies: In many Caribbean and Pacific island nations, the US dollar is accepted by hotels, tour operators, and restaurants even if the official currency is local. This is a practical arrangement, not a legal one.
• Border regions: In areas near a stronger economy, the neighbour’s currency may circulate freely. For example, the euro is commonly accepted in non‑eurozone countries bordering the eurozone, such as Switzerland and Montenegro (though Montenegro unilaterally adopted the euro as legal tender in 2002 without a formal agreement, 2025, ECB).

When researching a country, always check two sources: the IMF’s Annual Report on Exchange Arrangements and Exchange Restrictions for the official legal‑tender list, and the US State Department’s Investment Climate Statements or the UK FCDO travel advice for descriptions of what is actually used on the ground.

Practical checklist for country comparison

When you see a currency listed for a country, apply this checklist:

• [ ] Identify the issuer, central bank or monetary authority (source: IMF or the country’s central bank website).
• [ ] Check if the currency is shared, does the same currency name and code appear for another sovereign state? (source: IMF list of exchange arrangements).
• [ ] Check for unilateral adoption, does the country use a foreign currency without a union treaty? (source: IMF).
• [ ] Check for unofficial use, do travel advisories, news reports, or the US State Department’s Investment Climate Statement mention widespread use of a second currency? (source: foreign ministries, 2025).

Why this matters for comparison

A single GDP per capita figure for a country using a foreign currency does not capture the monetary‑policy constraint. For example, Ecuador uses the US dollar and has no central bank that can print money, its monetary policy is set by the Federal Reserve in Washington. This matters when comparing Ecuador to a country with its own currency and flexible exchange rate, like Colombia. The same GDP per capita number tells you about output, but not about the country’s ability to respond to economic shocks.

Similarly, a monetary union like the eurozone means that all member states share the same interest rate and exchange rate, but their fiscal policies (taxation, spending, debt) remain national. This is why comparing unemployment rates across eurozone members (e.g., Germany vs. Greece) reveals national labour‑market differences, not monetary differences.

Summary table of major currency groups (2025, IMF)

Currency	Number of countries/territories	Type
Euro	20	Formal monetary union (ECB)
West African CFA franc	8	Formal monetary union (BCEAO)
Central African CFA franc	6	Formal monetary union (BEAC)
Eastern Caribbean dollar	8	Formal monetary union (ECCB)
CFP franc	3	Formal monetary union (IEOM)
US dollar (sole legal tender)	7	Unilateral adoption
Australian dollar (sole legal tender)	3	Unilateral adoption
New Zealand dollar (sole legal tender)	4	Unilateral adoption
Indian rupee (sole legal tender)	3	Unilateral adoption