Since last year, the government has talked about tapping so-called kyumin koza to help fund reconstruction in the areas hit by the March 11 disaster. Kyumin koza are "sleeping bank accounts," meaning savings in financial institutions that have gone untouched for long periods of time. The government says it needs at least ¥50 billion for reconstruction, and every year banks "uncover" about ¥80 billion in unclaimed accounts, 90 percent of which contain less than ¥10,000 each. For banking purposes the definition of a kyumin koza is an account from which no transactions have been carried out for ten years and whose holder the bank has not been able to contact.
Under such circumstances, banks typically move this money into the plus column on their books, which is why the financial industry isn't too crazy about the government's plan to commandeer the comatose cash. The banks' argument is that even though they have taken over this money, if the account holder does show up with proper identification and other pertinent documentation they will happily return it; but they couldn't do that if the government has taken it first.
It's a credible argument, though Japanese weekly magazine Gendai points out that ever since the end of the bubble era in the early 1990s, banks have become very strict about closing bank accounts, meaning that someone who had not touched their money for more than 10 years would probably require a lot of paperwork to prove the account was his. It would thus be very difficult for individuals to access accounts of family members who have died, since those individuals would have to produce death certificates, proof of relationship and other documents. Moreover, an account can only be closed at the branch where it was opened. It's assumed that a large number of sleeping accounts have gone untouched because the account holder died without informing his or her family of its existence.