Handling foreign currency invoicing

[Tom Vincent]

Following the [Using Multiple Currencies][1] section of the GnuCash
FAQ, I've set up some accounts as follows:

Accounts Receivable:GBP
Accounts Receivable:HKD

Sales:GBP
Sales:HKD

I've then created a customer whos billing currency is HKD and created
and posted an invoice with single entry of 1000 HKD (see the first
attachment for a test fixture).

Now when I come to pay the invoice, I choose checking account (GBP) as
the transfer account and GNUCash prompts for the conversion rate.
After entering 80 in the 'to amount' field, my ledger now unexpectedly
looks as follows (see the second attachment):

Assets 12,500 GBP
Assets:Accounts Receivable 11,500 GBP
Assets:Accounts Receivable:GBP 0
Assets:Accounts Receivable:HKD 920
Assets:Current Assets:Checking Account: 1000 GBP

Income 12,500 GBP
Income:Sales 12,500 GBP
Income:Sales:GBP 0
Income:Sales:HKD 1000

This seems to be because I misinterpreted the conversion dialog, not
noticing I was transferring *from* GBP to HKD.

1. How can I undo this?
2. If I revert to attachment 01, and instead fill the exchange rate
field with 12.918 (1 GBP = 12.918 HKD), the income accounts are as
expected, but now Assets:Accounts Receivable:HKD has a total of
-11,918 (see attachment 03), with the following transactions:

Payment (Split Transaction) 1000
Pre-payment (Split Transaction) 11,918
Invoice (Income:Sales:HKD) 1000

Where am I going wrong?

  [1]: http://wiki.gnucash.org/wiki/FAQ#Using_Multiple_Currencies
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