Hi Alex,
There could be multiple reasons here.
1) When working with sales or purchase documents (e.g. Sales Order, Purchase Order) taxes can get calculated in two different currencies: the document currency and the reporting currency, the latter being the currency of the tax code country which is used for reporting. In case the document currency and the reporting currency differ, taxes are calculated in both currencies and the system needs a corresponding exchange rate maintained for the tax date(s) used in the business document.
2) There could be an approval process set up in the Different currency then USD. (Let's say EUR) which means when Purchase order is posted, system needs to convert the Purchase order values to EUR and then determine if document should go for approval or not.
3) In the inter-company projects scenario the customer's (maintained as account in sales order) information sent by the Sales Order is carried over into the Purchase Order. This error is being raised by the Tax Calculation while doing the tax calculation based on the delivery address. And the delivery address in this case is determined from the customer.
Could you please check this?
If you need further help, I suggest you to create an incident, so that we can have a look on system settings and investigate further on the root cause.
PS. Maintaining the exchange rate between USD/CAD for mentioned date will anyway remove the error message.
Regards,
Harshal