The rate of the transaction date: how we handle currencies

The most common question about multi-currency tracking is simple: "which exchange rate do you use?" Finance Flow 365's answer: the rate of the transaction date, and only that one. Here is what that means and why every other answer eventually breaks your books.

The problem: rates move, the past should not

Picture three currencies in one life: rent in euros, subscriptions in dollars, family support in a third currency. At the end of the month you want one number: total spent. To get it, everything must be converted into one currency. At which rate?

If it is today's rate, something unpleasant happens. You closed August, got your total, relaxed. Two weeks later the rate moves five percent and your August total silently changes, although nobody spent anything in August anymore. The spreadsheet that matched your bank statement yesterday no longer matches it today.

This is not a detail. Tracking runs on trust in your own numbers: the moment the past starts drifting, trust ends, and the habit of tracking ends with it.

The solution: the rate freezes at the moment of the operation

In Finance Flow 365 every entry is fixed in all tracked currencies at once, at creation time, at the historical rate of its own day. Bought something on August 5th? The August 5th rate is used. Forever.

An example. On August 5th you paid 100 euros for a hotel; the rate that day was 1.09 dollars per euro. The entry stores both 100 euros and 109 dollars. In September the rate hits 1.15. What changes in the entry? Nothing. The hotel cost 109 dollars on the day you paid for it, and that truth does not expire.

New expenses, meanwhile, use their own fresh rates. The past is stable, the present is current, and both are honest.

What this gives you in practice

Monthly totals never change retroactively. August, closed on September 1st, looks the same in December. Statements match the records. Comparing months finally means something: you compare spending, not exchange rate noise.

A separate bonus for anyone who has relocated: old expenses in the old currency stay meaningful. You see what something cost back then, in that money and at that rate, not a retroactively converted abstraction.

One more detail we consider non-negotiable: amounts are stored and added without rounding losses. Cents do not evaporate in conversions, so the yearly total adds up to the last digit.

If your life runs in two or more currencies, read the “Life in several currencies” scenario: the whole mechanism is shown there through the story of one actual move.