All official languages of the issuing authority, plus all that appear on the physical currencies. But exclude languages that appear on motto ("E Pluribus Unum", of the US, "Dieu et mon droit" of UK, if it ever appears) that are in such languages for historical reasons, and regional languages on rotation (the don't-be-stupid clause).
It is better missing than to guess. It is ok to be missing.
In some languages, indefinite/definite articles are part of the nouns, such as the North Germanic languages. Use indefinite singular form. Example: Faroese króna. After all, you wouldn't write "le franc français" in French franc's infobox, right?
One line per spelling. Use the {{native name}} or {{lang}} templates where appropriate. If hypothetically Australia, Spain and Portugal all use the Australian dollar, then the infobox would have
Use capitalization rule as if it is in the middle of a sentence in that language. For example, "franc français", not "Franc français", nor "franc Français".
Use symbol if possible. But it has to be correct down to the position and the spacing. If you are not sure, fall back to the full name. Central bank websites are a good source for authoritative information.
Correct:
$1, 10¢, £5, 500 Kč
Incorrect:
1$, $ 1, 10 ¢, ¢10, £ 5, 5£, 500Kč, Kč 500
If the symbol is behind the numeral, then put the symbol after the last one.
Use the representation on the coin/banknote, e.g. if it says "100 cents", then it's "100 cents", not "1 dollar"; if it says "½ franc", then it's not "50 centimes"
Use ½ and ¼, not 1/2 or 1/4
If the list involves both the subunits and the main unit, do not add a new line after the subunit. For example,
Recommended:
10p, 20p, 50p, £1
Not recommended:
10p, 20p, 50p £1
However, add a new line with <br/> after the subunit if and only if the total number of lines remains the same.
Recommended:
10p, 20p, 50p
£1, £2, £5
Not recommended:
10p, 20p, 50p, £1, £2,
£5
Do not put "and" before the last one, e.g. "1, 5, 10, 20, 50, 100 yuan", not "1, 5, 10, 20, 50, and 100 yuan"
For a large numbers, write like these
1000 (no space, no comma)
10 000 (with , not a regular space)
100 000 (with , not a regular space)
1 000 000 (with , not a regular space)
107 (or higher) (use {{e}} if the number doesn't start with 1)
Frequent v.s. rare comments:
Smallest coins:
recently and officially phased out (e.g. 10 and 20 h of Czech koruna, 5 New Zealand cents)
not used in practice because of small value (1 and 5 South Korean won (maybe it's official now...))
Denominations in the middle
Ask yourself this question: if you are given change when conducting a daily activity, and denomination X is required to make a mathematically minimal number of coins and banknotes. Would you receive denomination X? This applies to US 50¢ (historical reason about silver stuff in the 1960s) and 20 New Taiwan dollars (a new denomination lacks government support and campaign).
Banknotes that are being replaced by coins (I know this happens all the time, but I just can't think of one that is ongoing right now)
Large denominations
Ask yourself this question: do ATMs give this denomination. The answer is no for US$50 and US$100. This question also applies to denominations in the middle, e.g. ATMs in Iceland dispense 500, 1000, and 5000 króna notes, making 2000 krónur "rarely used"
Ask yourself this question: When someone buys an electronic that is worth several times of the largest and pays by cash. Is it more likely to use denomination X?
You might be thinking, "why do these simple words 'rare' and 'frequent' have to turn into these long definitions?" The bottom line is, these definitions have everything to do with the usage in daily life. And the issuance number quoted by the central banks/governments have little meaning in this sense, as a lot of them can be used for interbank transactions, hoarded by tax evaders and drug dealers (I hope this is not "daily life"), by casinos, and in the hands of foreigners.
And only use these attributes when you are very sure. If you are not, fall back to a single list where rarely and frequently are not distinguished.
