A unit of account is the standard measure an economy uses to express the value of goods, services, and debts in consistent numbers, and examples of a unit of account fall into three broad groups: fiat currencies like the U.S. dollar, the euro, and the British pound; historical commodities such as silver weights, cowry shells, and salt; and modern digital assets, including cryptocurrencies like Bitcoin and dollar-pegged stablecoins. Each of these has functioned as a shared yardstick for pricing, though only the dollar counts as an official unit of account for U.S. tax and legal purposes.
What Qualifies Something as a Unit of Account
Before running through the examples, it helps to know why they qualify. A workable unit of account has three traits. It must be divisible into smaller pieces, so you can price a stick of gum and a house using the same system. The dollar breaks into 100 cents; Bitcoin breaks into 100 million satoshis. It must be fungible, meaning any one unit is interchangeable with any other. And it must be countable, so you can add, subtract, and compare values with ordinary arithmetic.
Anything that meets those three tests can serve the function. Anything that fails one of them cannot, which is why unique collectibles or partly damaged goods make poor measuring sticks even when they hold value.
Fiat Currency Examples
The U.S. dollar is the textbook case. Federal law designates U.S. coins and currency, including Federal Reserve notes, as legal tender for all debts, public charges, taxes, and dues.1Office of the Law Revision Counsel. 31 USC 5103 – Legal Tender The same statute excludes foreign gold and silver coins from that status. So the dollar is not merely convenient; it is the unit the federal government requires when you settle an obligation like income tax.
The euro and the British pound play the same role in their respective economies. A German grocer prices bread in euros. A London landlord quotes rent in pounds. Which currency an economy picks matters less than the fact that everyone inside that economy agrees on the same one. The shared agreement is what lets a single number on a price tag communicate value to millions of people at once.
Because currencies do not translate themselves, the U.S. Treasury publishes official exchange rates on a quarterly basis so government agencies can convert foreign amounts into dollars for reporting.2U.S. Treasury Fiscal Data. Treasury Reporting Rates of Exchange If market rates drift more than 10% from the published figure, the Treasury issues an amendment. Every cross-border transaction eventually runs through a conversion like this.
Historical and Commodity Examples
Long before paper money, people still needed a way to say “how much.” Ancient Mesopotamian merchants used specific weights of silver. West African traders used cowry shells. Roman soldiers were paid partly in salt, which is where the word “salary” comes from. In each case, the commodity itself was the unit of account: prices were quoted in shells, grain measures, or metal weights.
These systems worked because the commodities were divisible, fungible, and countable. What limited them was practical. Hauling sacks of grain or bars of metal is inconvenient, and commodity values swing with harvests and mining output, which makes the yardstick itself move. Paper and digital currencies solved the portability side. Central banks try to solve the stability side through monetary policy.
Digital and Virtual Currency Examples
Cryptocurrencies function as units of account inside their own ecosystems. On many decentralized applications, prices and fees are quoted in the network’s native token rather than in dollars. The IRS defines virtual currency as “a digital representation of value that functions as a unit of account, a store of value, and a medium of exchange,” and classifies it as property rather than currency for federal tax purposes.3Internal Revenue Service. Frequently Asked Questions on Virtual Currency Transactions That property classification has real consequences at tax time.
Stablecoins sit between crypto and fiat. Each one is pegged to a fiat currency, usually one-to-one with the dollar, which makes them a more predictable unit of account for digital commerce. A business quoting a contract in a dollar-pegged stablecoin does not have to worry about the price moving 10% between agreement and settlement. For platforms built on blockchain infrastructure, stablecoins offer a way to keep books in a familiar denomination while operating in a decentralized system.
How Inflation Changes What a Unit of Account Is Worth
The label on a unit of account stays constant. What it buys does not. A $50,000 salary in 2010 and a $50,000 salary in 2026 read the same on paper but support very different standards of living. This is the tension between the unit-of-account role and the store-of-value role: the ruler stays marked in the same numbers even as the substance behind each number shifts.
Long-term contracts often handle this with escalation clauses tied to the Consumer Price Index. The Bureau of Labor Statistics publishes guidance on how to build these adjustments into rent, wages, alimony, or child support agreements.4Bureau of Labor Statistics. How to Use the CPI for Contract Escalation The basic calculation divides the change in the CPI between two periods by the earlier period’s index value, then multiplies by 100 to get a percentage. Some contracts add caps limiting how much a payment can rise, or floors guaranteeing a minimum adjustment.
Treasury Inflation-Protected Securities take a different approach. TIPS adjust their face value each month based on CPI changes, so the unit of account for the bond itself moves with inflation. At maturity, investors receive whichever is higher: the inflation-adjusted principal or the original face value. Interest payments are calculated against the adjusted principal, so they grow with the price level rather than being eroded by it.
What Happens When Your Unit of Account Is Not the Dollar
Any time you earn, hold, or transact in a unit other than the U.S. dollar, the IRS still expects everything reported in dollars. How the conversion works depends on what kind of non-dollar unit you have.
Foreign currency gains and losses on transactions like settling a contract in euros or repaying a loan in yen are generally treated as ordinary income or loss, computed separately from the underlying transaction.5Office of the Law Revision Counsel. 26 USC 988 – Treatment of Certain Foreign Currency Transactions The gain or loss is measured by the exchange rate change between the date the transaction was booked and the date payment was made. Some taxpayers can elect capital gain or loss treatment for forward contracts and options, but that election has to be identified before the close of the day the transaction is entered into.
Cryptocurrency works differently. Because the IRS classifies virtual currency as property, selling or exchanging it triggers capital gains or losses rather than the ordinary treatment that applies to foreign currency.3Internal Revenue Service. Frequently Asked Questions on Virtual Currency Transactions Even swapping one cryptocurrency for another is a taxable event. If you receive crypto as payment for goods or services, the fair market value at the time of receipt counts as ordinary income, as if you had been paid in dollars.
Bartering follows a similar logic. When you exchange services or property without any currency changing hands, you still owe tax on the fair market value of whatever you received. If both parties agreed on the value in advance, the IRS generally accepts that figure. Barter exchanges report these transactions to the IRS on their own, so the agency knows about them whether you report them or not.
The through-line across all of these rules is simple. Plenty of things can function as a unit of account in daily life, from euros to Bitcoin to a bushel of grain traded between neighbors. Only one of them counts when you file with the IRS.