What is a hanko, or an official stamp? Without one of these (actually more than one), we could not do business in Japan. Without a hanko you can not open a bank account. Without a hanko we can not deregister and apply for export certificates for the cars we export. Every loan and contract with a bank in Japan is done with a hanko. Every company in Japan has more than one official hanko. The ONE official hanko must be registered with the local city office. Every official transaction we do with a car (name change or deregistration) must come with the hanko stamp as well as proof from the city office (proof of official hanko document) that this is our official stamp. When we stamp a bank document with the official stamp, the bank will place the proof of official hanko document over that stamp and flash it back and forth 10 or so times to check the document is the same stamp as our stamp.
Your hanko is worthless and valuable. Worthless as you can not sell it, it has no value and no one would buy YOUR hanko. Valuable as you use it for everything: car name changes, deregistration, contracts, sale and purchase of real estate. If you loose it, there is a lot of red tape to get a new one.
Although there is the official hanko, or JITSUIN, there is also a “bank hanko”, if you want to withdraw money from the bank or anything “official” with the bank, that is not contractual. Contract means your registered hanko, while just normal bank business: bank hanko.
