From a question I asked earlier (Difference between "NG" and "QB" domain IDs), I was under the impression that the NG and QB ids are interchangeable for records created in the cloud. Does this remain true for the new V3 API?
When I try to send an Invoice create request that contains a cloud-created line item's QB id, I'm getting this error:
<IntuitResponse time="2013-10-31T15:11:30.185Z" xmlns="http://schema.intuit.com/finance/v3">
<Fault type="Validation">
<Error code="0">
<Message>Operation failed with errors: Invalid field value ItemRef: Invalid ItemAll ID: [QB:5]</Message>
</Error>
</Fault>
</IntuitResponse>
Yes, an object created in V3 in cloud has an NG id and this does not changes even after sync. In the same way, an object created in QB desktop company file has a QB id and does not change even after writeback. You cannot interchange and use them in V3