A valid unused ticket can be changed only once to a different ticket of the same category without any handling charges, but there are some exceptions.
Any difference in price will be collected when the change is made.
If a second change is necessary, a new ticket must be purchased;
the previous ticket can be refunded at a station or travel agency, with deduction of a handling charge.
A reserved seat ticket can be changed only before the departure of the train on which the original seat was reserved. The ticket is not valid after departure of that train.
A change of a reserved seat ticket can be made at any JR reservation ticket office during its business hours.
A change of a ticket purchased from a travel agency with a credit card can be made by the same travel agency or by any JR East stations.
Change After Start of Trip
A ticket can be changed after the start of the trip; any additional fares or charges involved must be paid, but previously paid fares or charges will not be refunded except for fare tickets with an unused segment of at least 101km.
Missing a Train
Reserved-seat tickets and Green Car tickets are not valid after departure of the train specified, and no refunds can be made.
The holder of a reserved seat ticket who has missed the train is entitled to be seated on a non-reserved seat on a later train on the same day. The full charge must be paid, however, if a reserved seat on a later train is used.
Any unused, valid ticket can be refunded after deduction of the specified cancellation charge.
A ticket purchased from a travel agency with a credit card may be cancelled through the same travel agency.