Sale and Authorization transactions can make use of a reference transaction as a source for transaction data. PayPal looks up the reference transaction and copies its transaction data into the new Sale or Authorization transaction. With the exception of currency amount data, which triggers a filter if out of range, reference transactions are not screened by Fraud Protection Service filters.
When PayPal looks up the reference transaction to obtain the transaction data to be used by the new Sale or Authorization, neither the reference transaction nor any other transaction in the database is changed in any way. That is, a reference transaction is a read-only operation - only the new transaction is acted upon.
For more information, refer to Fields Copied From Reference Transactions. You can also see a Sample Reference Transaction.