Multi currency invoicing (bug 715123)

[Christian Stimming]

Am Dienstag, 3. Dezember 2013, 23:29:11 schrieb Geert Janssens:
> And there's my point of uncertainty: what amount would make most sense
> to the user to see for a conversion:
> 
> - the amount of one single entry, with or without tax included ?
> - the total amounts for each currency as they appear on the invoice ? In
> the example that would mean the sum of the three USD entries, possibly
> with tax if tax is in the same currency. If tax is in yet another
> currency another exchange rate would be asked for the total amount of
> all taxes in that currency.
> 
> For me the second option makes more sense.

Yes, for me too.

> Note particularly in the second option that currently it's possible to
> have entries in invoices for which the referring account's currency is
> different from the accounts' currencies in the tax tables. I'm not sure
> if there is any real world use case for this, but the code doesn't
> restrict this. You can currently even create one tax table with accounts
> in several currencies, so for one invoice entry you could end up with an
> invoice currency, and entry account currency and several tax table
> account currencies all being different.
> 
> So the second question would be: how flexible should gnucash be to still
> be practical and not overly confusing ?
> For example, would there exist real world situations where a tax table
> should support accounts in multiple currencies ?

In general I think currently gnucash allows rather too much flexibility. 
Traditionally we've allowed pretty much everything that could be mapped to the 
data structures. I think this is overdone in some cases, such as here. 
Instead, we should better define the use case, then allow the multi-currency 
combinations that make sense within the defined use cases, but disallow other 
combinations. 

In this sense I'd vote to restrict tax tables to one single currency, and also 
add further restrictions on the accounts for invoice entries. I'm not sure how 
to clearly define what sort of multi-currency should be allowed and what 
should not, though.

Regards,

Christian