Can someone please explain how I can 1) safely remove duplicate expenses showing up as outstanding credit card items AND 2) reverse the invoice and billing charges?

Sorry, Authentication keeps failing when I post to the answer from Julia.
Example:  Some receipts were uploaded twice.  The expense was picked up twice by QBO.  Management sent two invoice line items as billable expenses with a 15% handling fee markup.  A company paid both duplicate billable expenses.  Where can I find information on how to properly deduct the excess amount charged as billable expenses with a 15% markup on the management invoice and paid on the individual company bill?  Does this affect the credit card outstanding item reconciliation?  What can be done to remove the duplicate items from the credit card reconciliation?   What may be done to prevent the duplicate receipt items from occurring?  (Some are input errors by staff).   Thank you!

Julia,
Good explanation of how to find the duplicate entry and delete it.
What will deleting the transaction do besides getting rid of it? 
Example:  Does this reverse the already billable expense transaction for $45.16 plus 15% markup charged on an invoice from Management to Capital Two for $51.93?  (Management pays all bills and charges a 15% markup fee to the company.) Capital Two paid $51.93 back to Management as part of the bill total owed Management.  How may this $51.93 be credited back to Capital Two?
How can this credit be applied in QBO?  This transaction happened in a prior month (June) and normally the invoices are charged in the month occurred.  Can this credit be applied to September invoice charges?
How does this affect the vendor listing of billable expenses for that Payee?  Does QBO do a reversal of the entry made into the vendor listing?
Thank you.
 
Mark