Tracking number already assigned to another transaction

[myeheyaccount]

Hi,

I sold an item under my account and my wife did under her account to the same buyer on the same night. I packed both items in one box amd printed a USPS shipping label under her account which marked the item as shipped and added the tracking number to her sale.

I then logged into my account and marked my item as shipped and tried to manually add the tracking number. I got a message stating the tracking number was already assigned to another transaction. It would only cost me an extra $2.60 to send a second box to the buyer, but that seems silly. I don't want my account to take a negative strike for not uploading tracking either.

Thanks!