If you get too much change back from a big chain store, you're likely to keep it.
Defense contractors are no different.
In addition to overpayment problems, DOD's billing is beset by inefficiencies including time wasted maintaining separate billing codes for closely related items, matching documents manually and computer system incompatibility. DOD also maintains misleading and needlessly specific records. In comparison to other non-federal billing contractors, DOD's billing system is highly inefficient. Processing a contract invoice costs DOD 14 times more than the private sector in direct labor costs. A private sector worker can process 16,400 invoices a year, while the average individual at DOD processes about 1,000 invoices per year.