MoneyWorks, like most of the small business accounting software, tag the currency to a name. You have to create as two creators instead of one if a creditor traded with you in both foreign (such as USD) and local currency (SGD).
You can easily offset an invoice with a credit note from the same supplier (or customer) if they are in the same currency. You can either use the contra feature from the command menu or a payment transaction to offset it. However, if both invoice and credit note is in a different currency, then have to consider using a contra account to clear them instead.
Assuming you have:
First, you create a current liability account (you can use current asset if you preferred) and name it as ‘contra’. Then, create a dummy:
Next, use the contra feature (from the command menu > Adjustment) to offset:
I, usually, prefer to use the same document number (maybe add a – behind the reference number to differentiate it) and a memo in the description for audit purpose.