Usually the stamps already in use in that country are overprinted with some identification to mark them as being used in the new country. Such is the case with Bangladesh. Bangladesh was formerly East Pakistan, and when they gained their independence and renamed their country, they used the stamps of East Pakistan with an overprint declaring the name of the new country.

These are provisional stamps, and usually provisionals are very costly, since they are used only in an emergency period, being replaced by stamps definitive to the country at the earliest opportunity.