There are now two issues involved in this thread:
- Whether any currency is shown, and
- Whether $-designated currencies can be distinguished from one another.
@pjy, in your initial post you said currency is not shown. That only occurs if no base currency has been set. To remedy that, select a Base Currency under Settings. In your case, this would presumably be the Australian dollar. Once your base currency is set, you can denominate customers in their own currencies, if you want. In your example, your US customer’s invoices would then be in US dollars.
@Brucanna raises the issue of telling them apart. Manager used to show a full, 3-letter designation for all currencies wherever they occurred on transactions or reports (USD and AUD in your example). But many users complained about this because of the clutter it added. The symbol is one of most, if not the most, used currency symbols in the world. Yet most Manager users operate only in their local currency and didn't want the extra clutter. So the program was changed to show only the symbol for any currency using it.
That’s the explanation for why things are like they are. The downside is that when dealing in foreign currencies, a note is now appropriate explaining which currency the transaction is in, which currency should be used for payment, etc. That might be an extra step. But personally, I think it is always worth it to prevent confusion, even in cases where the program uses the 3-letter currency abbreviations. It avoids having to ask for reissuance of payments, bank charges for foreign currency conversions, and customer anger when the dollars are not equivalent and you have to notify them after the fact of what seems like an increase in an invoice. This is just my opinion, but I think there are already enough aggravations built into multi-currency business relationships to rely on just a currency symbol or designation.