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Question: Why GetItemTransactions or GetSellerTransactions API calls return TransactionID=0?
Answer: When an item is listed as a Chinese auction type ( the default value of the AddItem.Item.ListingType property), the TransactionID always returns a value of '0' as described in the online document : http://developer.ebay.com/DevZone/XML/docs/Reference/eBay/GetItemTransactions.html
"For Chinese auctions listings (single-item listings for which there can be only one transaction), TransactionID is always 0 ..."
TransactionID is returned in several APIs : GetItemTransactions