Currency formatting for transactions in another country's currency

Question

This is a really simple question, but the answer is stumping me: How do you format another country's currency correctly?

Specifically, this answer, quoting from Wikipedia, has a great survey of how various countries format large numbers in their system:

In English Canada, Ireland, Israel, Japan, Korea (both), Malaysia, New Zealand, Singapore, Taiwan, Thailand, the Philippines, the United Kingdom, and the United States: 1,234,567.89 or 1,234,567·89; the latter is generally found only in older, and especially handwritten, documents. Australia used this style up until the 1970s; now it uses the SI style

In Mexico: 1'234,567.89; for million separator an apostrophe is used.

In India, due to a numeral system using lakhs (lacs) (1,00,000 equal to 100 000) and crores (1,00,00,000 equal to 10 000 000), comma is used at levels of thousand, lakh and crore, for example, 10 million (1 crore) would be written as 1,00,00,000.

Assuming I conducted a transaction for $4,999,999.99 in the US system of formatting, using USD for the currency. If this transaction is later viewed in a version of my site localized for Mexico, do I display it as $4'999,999.99 to match their number formatting? $4,999,999.99 to match the original currency? In India, would it be $49,99,999.99?

Related: Would the currency symbol follow the country's conventions for placement, or would it always be in front (as is the standard for USD)? What about negative values?

Answer 1

The designation of a sum of money should be formatted according to the conventions of the language (and culture) used in the context otherwise, i.e. in the application, document, web page, or other context. E.g., if an application uses French as the user interface language, then any sum of money should be displayed according to French conventions, no matter what the currency is.

It can be difficult to get reliable data on such conventions, but CLDR is generally a good starting point, and there are software libraries that implement part of CLDR definitions in some programming languages.

Things to be localized include the decimal separator, the grouping principles, the group separator, the placement of the currency with respect to the number, the currency designators (symbols, abbreviations, or names), and the notation of negative numbers.

Answer 2

Interesting question.

About Mexican currency formatting

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I was curious about the Mexican way to use an apostrophe as a separator so I've done some research, discovering interesting things:

1. If you google the sentence quoted in the quote ("In Mexico: 1'234,567.89; for million separator an apostrophe is used") you come up with only 47 results.
2. The most (apparently) reliable of the 47 results is the Kenyan Wikipedia page about "Decimal Mark".
3. But on the English version of the same page there's no reference about Mexico using apostrophes as a separator.
4. On the contrary, on that page Mexico belongs to the group of countries using this formatting style: 1,234,567.89 (see table below, last row)

At this point I assumed the Kenyan page was wrong, but I wanted to double checked if the format "1,234,567.89" is really standard, so I've searched for reliable sources.

On page 30 of the "Spanish Style Guide" from Microsoft's Download Center you can find instructions for Mexican currency formatting:

At this point I think we can say that:

• in Mexico no apostrophe is used for million separator and
• to answer your question, you can keep the same format as US: $4,999,999.99.

About negative numbers

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According to this post:

The standard accounting way is always to show negative numbers in parentheses. If you want to appeal to primarily financial professionals, that's the accepted practice.

Where do I place the currency symbol?

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Even though I assume you're working (also) with non-European countries, you may want to have a look at this Wikipedia page, at the paragraph "Position of ISO 4217 code in amounts":

The ISO standard does not regulate either the spacing, prefixing or suffixing in usage of currency codes. According however to the European Union's Publication Office, in English, Irish, Latvian and Maltese texts, the ISO 4217 code is to be followed by a fixed space and the amount: a sum of EUR 30

as we can see on Amazon.co.uk:

In other languages it's just the opposite:

In Bulgarian, Croatian, Czech, Danish, Dutch, Estonian, Finnish, French, German, Greek, Hungarian, Italian, Lithuanian, Polish, Portuguese, Romanian, Slovak, Slovene, Spanish and Swedish the order is reversed; the amount is followed by a fixed space and the ISO 4217 code: une somme de 30 EUR

as we can see on Amazon.it:

I hope this will help.