When in School Website > Content > Giving > Giving Forms > View Online gifts, if you mark a transaction as Handled and click Update you get the message "Handling gifts will remove account number information." 

This warning message is left over from when our software used to store credit card transactions. 

All transaction data on giving forms is now sent directly through your Payment gateway and not stored in the School Website persona, so there is no information that is removed when handling a transaction. You will not lose any data by clicking Ok to dismiss this message.