The foreign currency definition is straightforward: foreign currency is any money issued by a country or economic region other than your own. For anyone based in the United States, the US Dollar is domestic currency and every other sovereign currency — Euro, Japanese Yen, British Pound, Swiss Franc, and the rest — is foreign. Each is issued and backed by its home country’s government or central bank, which guarantees it works as a medium of exchange within that jurisdiction.
What separates foreign currency from the cash in your wallet is exchange rate risk. The dollar value of any foreign currency shifts constantly. Hold 1,000,000 Japanese Yen today, and if the yen weakens against the dollar by 2% tomorrow, your holdings are worth roughly $130 less in dollar terms without anything else changing. That built-in volatility touches every international transaction, from a corporation paying overseas suppliers to an individual buying goods from a foreign retailer online.
How Exchange Rates Set the Dollar Value
An exchange rate is the price of one currency expressed in another. “EUR/USD 1.12” means one Euro costs $1.12. That single number determines the dollar value of foreign wages, investments, or imported goods at any given moment.
Most major currencies float, meaning the rate moves freely based on supply and demand. When global investors want more Euros, the Euro’s price in dollars rises; when demand drops, so does the rate. The Euro, Yen, British Pound, and Swiss Franc all work this way. Some countries take a different route and peg their currency to the dollar or another major currency. Hong Kong has maintained a peg to the US Dollar since 1983, with the Hong Kong Monetary Authority intervening to keep the rate within a narrow band of 7.75 to 7.85 HKD per dollar.
A spot rate is the price for exchanging currency right now. A forward rate is a price locked in today for an exchange that will happen at a set future date. Businesses use forward contracts to remove uncertainty about what a future payment will cost. If a US company owes a European supplier €500,000 in six months, a forward contract fixes the dollar cost of that payment.
The gap between the forward rate and the spot rate reflects the interest rate difference between the two countries. If US interest rates are higher than Eurozone rates, the forward price of the Euro will typically be slightly higher than the spot price, a forward premium. The reverse produces a forward discount. This relationship, called interest rate parity, keeps the forward market roughly in line with what an investor could earn in either currency’s home market.
What Conversion Actually Costs
Converting currency is never free, even when a service advertises “no fees.” The cost hides in three places.
- Most banks and exchange services build a markup into the exchange rate itself, so the rate you receive is slightly worse than the interbank “mid-market” rate that major institutions trade at.
- Flat transaction fees for international wire transfers at major US banks run from roughly $25 to $50 per transfer.
- Intermediary banks that route the transfer through the SWIFT network may deduct their own fees from the amount in transit, often without advance notice.
The total cost depends on the method. A bank wire with a $45 fee and a 1% rate markup on a $10,000 transfer costs about $145 all-in. Online transfer services often charge lower flat fees but apply a percentage-based commission instead. For smaller amounts, airport currency kiosks and hotel exchange desks are consistently the most expensive option, sometimes marking up rates by 5% or more. Compare the effective exchange rate you receive against the mid-market rate, not just the advertised fee.
Hard Currency and Soft Currency
Currencies are informally classified as “hard” or “soft” based on their stability, liquidity, and global acceptance. Hard currencies hold their value reliably, trade in deep liquid markets, and are widely accepted for international contracts. The US Dollar, Euro, Swiss Franc, British Pound, and Japanese Yen are the textbook examples. When a commodity contract or sovereign bond is denominated in one of these, both sides trust the unit of account will stay relatively stable.
Soft currencies are more volatile, less liquid, and harder to use outside their home country. Many developing-economy currencies fall into this category, often because the issuing country faces high inflation, political instability, or capital controls. Businesses earning revenue in a soft currency face amplified exchange rate risk when converting back to dollars, which is why long-term international contracts almost never use soft currencies as their denomination.
How the IRS Taxes Foreign Currency Gains and Losses
This is where foreign currency gets complicated for US taxpayers. Under Section 988 of the Internal Revenue Code, any gain or loss from a foreign currency transaction is treated as ordinary income or loss, not as a capital gain or loss. Ordinary income is taxed at your regular income tax rate, which can be higher than capital gains rates.
Section 988 applies broadly. If you hold Euros in a foreign bank account and the Euro appreciates against the dollar between when you acquired those Euros and when you spend or sell them, the gain is taxable as ordinary income. The same logic works in reverse: if the Euro weakens and you convert at a loss, that loss offsets ordinary income.
There is one important exception for individuals. Personal transactions — everyday purchases you make while traveling abroad or buying foreign goods for personal use — are exempt from Section 988 as long as the gain on any single transaction does not exceed $200. If you exchange $500 for Euros before a vacation and the Euro strengthens so that your leftover Euros convert back to $520, that $20 gain falls under the $200 threshold and you owe nothing. But if a currency swing produces a gain above $200 on a personal transaction, the full amount becomes taxable.
Taxpayers who trade currency through forward contracts, futures, or options can elect to treat those gains and losses as capital rather than ordinary, but only if they identify the election before the close of the day they enter the transaction. Without that election, ordinary income treatment is the default.
When You Have to Report Foreign Currency Holdings
Holding foreign currency in accounts outside the United States triggers two separate federal reporting obligations that many people overlook. The penalties for missing either filing can dwarf whatever the foreign holdings are worth.
FBAR (FinCEN Form 114)
Under the Bank Secrecy Act, any US person with a financial interest in or signature authority over foreign financial accounts must file a Report of Foreign Bank and Financial Accounts when the combined value of those accounts exceeds $10,000 at any point during the calendar year. The filing goes to FinCEN, not the IRS, and is due April 15 with an automatic extension to October 15. The threshold is aggregate. Three accounts holding $4,000 each puts you over the line.
Penalties for non-willful violations can reach over $16,000 per form. Willful violations carry penalties of the greater of roughly $165,000 or 50% of the highest account balance, per account, per year. Criminal penalties can include fines up to $250,000 and imprisonment.
FATCA (Form 8938)
The Foreign Account Tax Compliance Act created a separate reporting requirement filed with your tax return. If you live in the US and are unmarried, you must file Form 8938 when your specified foreign financial assets exceed $50,000 on the last day of the tax year or $75,000 at any point during the year. Married couples filing jointly have thresholds of $100,000 and $150,000. The penalty for failing to file starts at $10,000, with additional penalties accumulating for continued non-compliance after IRS notification.
FBAR and Form 8938 are not interchangeable. They go to different agencies, cover slightly different asset categories, and have different deadlines. Many taxpayers with foreign holdings must file both.
Digital Money Is Not Foreign Currency
Two developments blur the edges of what counts as currency, and both matter for how the rules above apply.
Central bank digital currencies are digital versions of sovereign money issued directly by a central bank. More than 130 countries are exploring or piloting them. China’s digital yuan is the largest pilot in the world, and the European Central Bank is advancing its own digital euro. These carry the same legal status as their physical counterparts. In 2025, President Trump issued an executive order halting all work on a retail digital dollar, making the US the only major economy to explicitly stop CBDC development. As foreign CBDCs roll out, US businesses and investors dealing with foreign counterparts may eventually handle digital versions of foreign currencies alongside traditional ones.
Stablecoins are a different matter. Despite being pegged to the dollar or other currencies, stablecoins like USDT and USDC are not treated as currency for US tax purposes. The IRS classifies all virtual currency, including stablecoins, as property. Every time you use a stablecoin to buy something, you technically have a taxable event, just as if you sold stock. The IRS has been explicit that virtual currency does not generate foreign currency gain or loss under federal tax law. The GENIUS Act, signed into law in July 2025, established a regulatory framework for “payment stablecoins” requiring issuers to maintain reserves and register with federal or state regulators, but it did not change the tax classification. Until Treasury issues new guidance, every stablecoin transaction remains a potentially taxable disposition of property.