Subject: The meaning of the currency fields in an invoice
On a paper invoice it is not uncommon to find unqualified numbers, no units or denominations and the reader has to guess what they mean. This leads to confusion and is a Bad Thing(TM).
In UBL, quite correctly, all numbers that are not simply counts have units/denominations, so we always know what they mean. And for the avoidance of doubt the currencyID in an Amount object is required. And the list from which these currencyIDs are drawn is defined in the Amount object definition as being UN/ECE Rec9.
Even the PaymentMeans/PayeeFinancialAccount has a currency code built into it so we know what currency the payment should be made in.
So what would it mean if any of the ???CurrencyCode fields in an Invoice were set. If they are the same as the relevant Amount/currencyId values then they are at best redundant, but what would/could it mean is they were different? And if they were different which has priority?
In short, I suppose what I am asking is if these ???CurrencyCode fields have any possible meaning and if not if they should simply be not specified when building UBL objects and ignored when reading them.