...
d) The order number must be unique for a specific customer. If you try to submit two different transactions with the same order number but a different customer_taxid, our server will respond with the message "Duplicated order.". Our server will also respond with "Duplicated order." if you try to re-submit an order that is already paid. If parameters order and customer_taxid are equal to a previously submitted unpaid order, the previous order will be updated with the new information provided and the response will be the URL to view/print the Boleto Bancário (
see note "c").
Characters allowed in the parameter order (regular expression): [a-zA-Z0-9\.\-\_\/]
...