Using a currency amount such as $1,000 in writing that has an international audience may be confusing (as may £1,000). This amount might represent US, Canadian, Australian or some other currency. I have taken to using the ISO currency codes, such as, USD 1,000, AUD 500, GBP 1,200 to avoid any confusion. Is this a good practice or are there alternative approaches?
I work for an investment firm, and we generally use ISO currency codes to represent currency.
You could have the following problems if you use currency symbols instead of ISO codes:
That said, if the context is clear and you do not need to represent different currencies, it may be easier on the reader if you use the currency symbol of their country.
I would be interested in reading the other responses you get to this question. We use the Chicago Manual of Style, and as far as I know, it does not give a definitive answer either.