Multi-Currency Accounting at a Currency Exchange — Each Currency, a Separate World

In an ordinary business, everything is measured in one currency; sales, purchases, expenses and profit are all in the local currency. But a currency exchange falls outside this rule. An exchange buys, holds and sells several currencies at once, and each of these units has a value that changes every day — sometimes every hour. For this reason, exchange accounting cannot be run with the mindset that "everything is local currency." Here each currency is a separate world and must have its own independent account, balance and position.

This article is about that foundational concept: why currencies cannot be mixed together, what a currency's balance means, what role revaluation plays, and where an exchange's real profit comes from. For a fuller picture you can also visit the complete guide to currency exchange accounting and operations.

Why can't currencies be added together?

Suppose your till holds 10,000 dollars, 5,000 euros and 200 million rials. If you try to "add" these up, the number you get is meaningless. Dollars, euros and rials are different kinds of things; just as if you tried to add kilograms, liters and meters together. The only meaningful way to compare them is to convert everything to one reference unit (rial, say) at the current rate — and that is exactly what is called "revaluation."

But the key point is this: revaluation is only a reporting view, not the reality of the balance. Your real balance is still those 10,000 dollars and 5,000 euros, not their rial equivalent. If the dollar rate rises tomorrow, the number of dollars you hold does not change; only the rial value of that same fixed number changes. For this reason, multi-currency accounting must keep two things at once:

• The nominal amount of each currency (how many dollars, how many euros, how many dirhams), which is the physical reality of the balance.
• The reference value (rial equivalent), needed only for reporting, comparison and profit calculation.

Software that does not separate these two layers will sooner or later go wrong; because it either loses the real balance or reports profit incorrectly.

Double-entry, this time for each currency

The backbone of any correct accounting is the double-entry ledger; every financial event has at least two sides, and the sum of debits and credits must always be equal.

At an exchange this principle does not change, but it adds one dimension: each currency has its own double-entry ledger. When a customer sells dollars and receives rials, two separate ledgers move at the same time; the dollar balance goes up and the rial balance goes down. These two are not separate events; they are two sides of one trade that must be locked together.

The point is that overall balancing, on its own, is not enough. In multi-currency accounting, each currency must balance separately. If your dollar ledger is off by 500 dollars, that difference cannot be "covered" by a surplus in euros; because the two are not interchangeable. Nexto software is built on exactly this logic; a double-entry multi-currency general ledger in which each currency's balance and turnover are held and balanced independently. If you want to go deeper, the currency exchange general ledger article explains this structure in more detail.

Currency position; the heart of an exchange's reality

When you keep each currency's balance separate, you arrive at a concept that may be the single most important number in the whole exchange: the currency position. Position means your net holding in each currency — after all the buying and selling, how many dollars or euros you ultimately have "open."

An open position means being exposed to the rate. If you have an open position of 20,000 dollars and the dollar rate rises by 100 tomans, then without making any trade at all you have become 2 million tomans richer — and if the rate falls, just as much poorer. This gain or loss is of a different kind than trading profit; it does not come from buying and selling, it comes from holding the currency amid market movements.

For this reason, a professional exchange must know at every moment what its position is in each currency. Nexto shows this position live and, at the end of each day, performs an overnight revaluation at the current rate so that the reference value of the balances is updated. We describe the precise mechanics of position and revaluation in currency position and revaluation.

Where does real profit come from?

Here we reach the most sensitive part. Many people think an exchange's profit means "the difference between the buy and sell rates." This is true, but incomplete. To know how much profit you made on a sale, you must know at what price you bought that currency — and when you have bought the currency in several rounds at different rates, there is no longer a single "purchase price."

The standard solution to this problem is the weighted average currency cost; that is, the cost basis of each unit of currency is calculated on the weighted average of all purchases, not the last purchase and not the first. Nexto maintains the cost of each currency with this very method so that when you sell, the real profit — and not an illusory profit — is calculated. This topic is so important that we have dedicated a separate article to it: weighted average currency cost.

So an exchange's total profit comes from two different sources that must not be confused:

Correct multi-currency accounting separates these two. Without this separation, on a day the rate has risen you may feel you did great work, while your trading profit was nearly zero and whatever there is came from the rate rising on a previously held balance — a profit that a single rate drop can evaporate just as fast.

Multi-currency tills and operational discipline

The multi-currency concept does not stay only in the ledgers; it also shows itself in day-to-day liquidity. An exchange usually has several tills and several accounts, and each may hold multiple currencies. Nexto supports multi-currency tills; meaning each till can hold the independent balance of several currencies at once, and the turnover of each currency in each till is tracked separately.

This discipline means you always know which currency, in which till, in what amount — and at period end you can produce a precise profit and loss report with Excel and PDF output that clearly shows trading profit and the revaluation effect.

Conclusion

Multi-currency accounting is not a matter of taste; the very nature of exchange work demands it. Each currency has its own nominal amount and reference value, each currency needs its own independent double-entry ledger and independent balancing, each currency's position must be seen live, and real profit only comes out right when the cost basis is kept with the weighted average. When these four principles sit together, an exchange knows where it stands instead of guessing.