We Japanese use seals (in Japanese, "Hanko") on many occasions. In fact, there are 2 types of seals: registered seals and personal seals.
Registered seals must be registered at the local administrative office (ex city office) where the resident lives to identify that the seals actually belong to the person registered.
In most companies, businessmen stamp their seals on documents they have made to signify that they will be responsible for the contents, or to stamp documents circulated to signify officially that they have taken a look at them. Thus, seals are necessary in business interactions.
Also, seals are used to express agreement in contracts, to give notices to government offices, to receive designated deliveries, etc. These days, signatures are also acceptable in receiving deliveries.
For general use, personal seals are adequate, but registered seals are required for important business documents, particularly financial transaction contracts.
