It is sometimes necessary to back-out or cancel an e-commerce transaction. Cancelling orders which did not go through or which were disallowed for one reason or another ensures that your Urchin reports, including Campaign Tracking reports, provide accurate information.
To cancel an order or transaction, find the transaction in your ELF or ELF2 log. Then, create a duplicate entry which contains a negative transaction total that cancels out the original transaction. For example, if the the original transaction total is $699, enter a duplicate entry with -699 dollars as the transaction total.
Read ELF & ELF2 Log Formats to understand the E-commerce log format that applies to you.