What steps should be taken to ensure all costs related to projects are being accurately accounted for?

A thorough review of the ledgers need to be done to ensure completeness of the data considered for project cost.

Developing checklists, for the various activities to be performed before closing books to determine project costs, would ensure accuracy of the cost. This would be added benefit if it is a recurring activity (monthly, weekly etc)

Ledger review needs to be done for identifying if any items of capital nature have been expensed as project cost.