Functions of money

Money performs four functions that every payments professional must be able to separate, because a payment can succeed on one function and fail on another. As a medium of exchange it removes the need for barter, so a buyer and a seller can settle without matching wants. As a unit of account it gives every price, invoice and balance a common measure, so a EUR 50,000 invoice and a EUR 48,250 credit can be compared and reconciled. As a standard of deferred payment it lets debts be written today and settled later, which is the foundation of credit, lending and supplier terms. Source: Bank for International Settlements, Committee on Payments and Market Infrastructures, payment system glossaries and primers. Why the four functions matter in practice is that a payment instrument can be strong on one and weak on another, and the weakness is where the risk sits. A volatile crypto asset may transfer value quickly, yet it fails as a unit of account when its price moves 10 percent in a day, so merchants price in fiat and convert at the point of sale. A closed-loop gift card is a medium of exchange inside one merchant, but it is not a general store of value, because it cannot settle a debt outside that merchant. When a business analyst writes requirements, naming which function is being relied on prevents a product from promising what its money cannot deliver. The parties to money are the issuer, the holder and the acceptor, and each carries a different risk. The issuer promises that the money will be accepted, the holder trusts that promise, and the acceptor takes the money in settlement of a debt. For central bank money the issuer is the central bank, and trust rests on the state and on the central bank balance sheet. For commercial bank money the issuer is a commercial bank, and trust rests on the bank, on deposit protection schemes and on regulation. A payment fails when any of these three parties stops trusting the others, which is why runs, freezes and refusals to accept are money problems, not just payment problems. A worked example makes the functions concrete. A manufacturer in Lyon owes a supplier in Munich EUR 120,000 for steel delivered on 30-day terms. The invoice states the amount in euros, which is the unit of account, and the 30-day term is the standard of deferred payment. On day 30 the manufacturer instructs a SEPA Credit Transfer of EUR 120,000, which is the medium of exchange in action, and the supplier holds the credited balance for a week before paying its own staff, which is the store of value. The euro worked because all four functions held at once, and the payment message, a pacs.008, carried the amount, the currency and the remittance reference that proved which obligation was settled. Failure shows what happens when a function breaks. In 2022 a bank in a sanctioned jurisdiction found its correspondent accounts frozen, so its customers held balances that were still a store of value on paper but could no longer act as a medium of exchange across borders. Domestically the same balances still bought goods, because local acceptors still trusted them, but internationally they were useless. A third failure is a failed settlement: a payment instruction is accepted, the debtor account is debited, but the creditor bank never receives settlement, so the medium of exchange moved in the books while the value did not. Each failure needs a different fix, and confusing them wastes the investigation. The effect on the bank, the customer and operations is direct. For the customer, money that cannot be spent, measured or stored is a broken promise, and the complaint is about trust, not about a screen. For operations, the form of money decides the ledger accounts, the reconciliation source and the failure playbook: central bank money reconciles against the central bank statement, commercial bank money reconciles against nostro statements, and e-money reconciles against safeguarded funds. A business analyst who cannot say which money a product moves cannot write correct requirements for balances, settlement, refunds or failure handling. For a business analyst, product owner or subject matter expert, the test is simple and must be applied to every new instrument. Ask which issuer stands behind the money, which of the four functions it performs well and which it performs badly, what asset settles the payment in the end, and what happens to the holder if the issuer fails. A payment product that cannot answer these four questions is not ready for a design review, however good its user interface looks. The Bank for International Settlements and central bank primers are the authoritative sources for these definitions, and they should be cited in the product record rather than paraphrased from a vendor slide. Money is also a legal concept, and the legal answer changes by jurisdiction. In the euro area the euro is legal tender, and Regulation (EU) 2024/886 governs instant euro payments; in the United Kingdom sterling is legal tender and the Bank of England issues banknotes; in India the rupee is legal tender under the Reserve Bank of India Act. A cross-border payment therefore moves between legal systems, and the payment message must carry enough data for each system to treat the money correctly. This is why ISO 20022 messages carry currency, amount, debtor, creditor and purpose as structured fields rather than as free text. Takeaway: money is not one thing, it is four functions performed by an issuer that others trust, and a payment is only as good as the money it moves. The four functions are medium of exchange, unit of account, store of value and standard of deferred payment. The issuer may be a central bank, a commercial bank or an electronic money institution, and each issuer carries different risk, different protection and different settlement. Before designing any payment product, name the money, name the issuer, name the settlement asset and test all four functions against a worked example and a failure. Last reviewed 7 November 2026.