A second currency: the one decision you can't postpone

The moment a second currency enters your records, the difficulty stops being arithmetic and becomes conceptual. Questions appear that have no single right answer. Which rate applies, the one from the purchase date or today’s? What belongs in the month’s total? Is exchanging cash an expense?

The awkward part is that getting any of these wrong doesn’t look like getting it wrong. The figures reconcile, the total displays, everything looks tidy. It’s simply incorrect, and nothing will tell you.

Most of these decisions can be revised later. One cannot.

Store the original amount

A transaction belongs in the currency it happened in. Twelve dollars is twelve dollars, not “roughly eleven euros.”

Two reasons, both serious.

Conversion is irreversible. Save only the converted figure and the original is gone permanently. Reconstructing it later from that date’s rate gives you an approximation of an approximation.

Rates move. A March total calculated in March and again in December will differ. With original amounts preserved you can recalculate at any rate whenever you like. Without them, never.

Hence the rule: conversion is a display layer, not a storage format. Everything else in this article can be redone later; a lost original amount can’t.

Which rate belongs in the total

There are three defensible approaches, and the right one depends on the question you’re answering.

The rate on the transaction date is the most accurate for history, since each purchase converts at its own day’s rate. Use it when you want to know what a trip genuinely cost.

Today’s rate for everything is simpler: the whole month converts at the current rate. It answers “what is this worth in my money right now,” but it distorts month-to-month comparison, because a difference can appear purely from currency movement rather than from anything you did.

The actual settlement rate is the most honest when you paid by card: your bank applied a specific rate and added a specific fee. The drawback is that you have to read it off the statement, since it usually isn’t available automatically.

The practical compromise: store originals, display the total at a recent rate, and remember that this total is an estimate rather than an accounting figure.

When there’s no rate

Not every currency pair has a reliable rate, and sources go down.

The correct behaviour is to exclude those amounts from the total and say so plainly. The total comes out incomplete, but you know it’s incomplete.

The worst option is counting them as zero. The total lands low, looks entirely normal, and you won’t catch the error now or in six months.

Exchanging money is a transfer, not an expense

Convert $200 into euros and you haven’t spent anything. The money changed form.

Record the exchange as spending and your month inflates twice: once by the exchanged amount, then again by whatever you buy with those euros. Double counting, and the invisible kind.

The only expense in that operation is the fee. Record that, if it’s material.

Travel deserves its own mode

Spending patterns during a trip differ enough that mixing them into an ordinary month is unhelpful — two weeks abroad will skew a year of statistics.

The working approach is simple. Record everything in the local currency without converting in your head. Don’t try to judge on the spot whether something is expensive, because it costs holiday time and comes out inaccurate anyway. Review the total after you’re home, when the actual charges have landed.

Three things are worth holding in mind, because they’re easy to forget and they move the total noticeably.

Currency conversion fees, typically 1–3% and sometimes more. On a $3,000 trip that’s $30 to $90, which is a dinner.

Cash withdrawal fees, often a flat charge plus a percentage. Five small withdrawals cost meaningfully more than one large one.

Dynamic currency conversion, or DCC. This is the terminal offering to charge you in your home currency instead of the local one. That rate is nearly always worse than your bank’s. Choose the local currency and let your bank do the conversion.

Reading a mixed total

A category holding three currencies needs careful reading.

Compare months within one currency. “Food was €340 in July against €410 in August” is a meaningful comparison. “Food €340 against $600” isn’t, even when an app adds them into a single number.

An approximate total is useful for a sense of scale and unhelpful for precise conclusions. If two months differ by under ten percent and rates moved during that time, there probably isn’t a difference at all.

What the app does

Voice Finance stores a transaction in the currency you recorded it in and never rewrites it when you change your base currency. A hundred thousand roubles stays a hundred thousand roubles even after you switch the base to dollars.

In the transaction list the original amount is shown first, with an approximate equivalent in your base currency beneath it, marked with ≈. When the currencies match, no equivalent appears — repeating the same number twice helps nobody.

Rates load independently of whether you have any transactions. The currency screen in Settings works immediately after install, shows when rates were last updated, and refreshes on demand. Without a connection it serves the last successful values, and amounts with no available rate are excluded from totals rather than counted as zero.

Recording in another currency works by voice too: “twelve dollars coffee” is understood as dollars. Phrasing details are in logging expenses by voice.

Where to start

If you’ve just acquired a second currency, do one thing: confirm your tool stores the original amount rather than a converted one.

The rest can be tuned as you go. Fitting a trip’s irregular costs into an ordinary plan is covered in building a monthly budget, and the basics of recording don’t change with the number of currencies — those are in how to track expenses.