NEC Corp. overcharged the Defense Agency a combined 63 million yen between 1997 and 2001 in five equipment contracts, according to internal agency documents obtained Monday by Kyodo News.

The agency later demanded that NEC return the overcharged amount. The firm complied after admitting its wrongdoing, but the agency did not disclose the case because NEC was a subcontractor, a senior agency official said.

The overcharge follows a similar case uncovered in 1999 in which the electronics giant padded expenses between fiscal 1991 and fiscal 1999 as part of a larger scam involving the Defense Agency's now-defunct Central Procurement Office.

According to the latest documents, NEC overstated expenses by 55.6 million yen between 1998 and 2001 for a 3.567 billion yen contract for Patriot missiles it received from another major electronics maker.

In doing so, NEC created two books on its computer and padded personnel costs, the documents show.

It also overcharged to the tune of 7.4 million yen in four subcontracts since 1997, including those for components of F-2 fighters and submarine steering systems.

Separately, NEC was asked to pay 86 million yen for delayed deliveries on five contracts for the agency's central command system and other equipment between March 2001 and February 2003, according to the documents.

NEC complied with the requests.

An official at NEC's corporate communications department said the company has refunded all overcharged amounts as requested by the agency, regardless of whether they concern direct contracts or subcontracts.

In the Central Procurement Office scandal, NEC padded bills by some 26.4 billion yen.