We had this issue once before (27/07/2010) where the order was placed via Google Checkout. We had two orders come through that were identical, however the later one when you view the receipt you see a screen that says
Code:
The specified order is no longer valid or is empty!
If this is an error, please contact us
When we view the order in Google checkout it says order was created and then another order number has been assigned. The new assigned order number is the one without a receipt.
We voided the duplicate order, the one that was assigned after the first order number, only to find it voids the whole order. We had to contact the customer and have him replace the order, to which the same thing happened.
This order has been dispatched yet the extra assigned order number is still there, claiming payment has not yet been captured when we take payment straight away and have already dispatched the goods.
We do not want to have to void this extra order as it may void the whole order again (despite this order been completed) as it may just confused the customer.
On 01/09/2010 (yesterday) we have had another google checkout that has duplicated by having another order number assigned to it. The extra order number is assigned within 5 seconds of the first order being created.
In short, customer places order with google checkout. Google checkout pay us straight away and give the customer an order number and conformation. Then 5 seconds later google checkout assigns another order number to the whole order (i.e. this may be order 106857 yet 106858 is also assigned to this order.) this is a rare issue but as we approach the busy period and with no answer or explanation as to why it happens we are worried.
The most important point is the order is not duplicated just assigned two order numbers.
I have contacted support about this, however this was when ver 8 was no longer supported so maybe we might find a solution.
Any help is massively appreciated.