Abstract: In a method of providing safe control, storage and transportation of banknotes there is used a closeable cassette (1) provided with locking means, said cassette containing a liquid-dye container (9) which is activated when an attempt is made to force the cassette, thereby to render the banknotes unusable. To prevent a successful robbery against, for example, a store or like place in which banknotes are introduced into the cassette with the aid of a special infeed unit (19, 20), the cassette is constructed so that it can be removably connected to said infeed unit while exposing an infeed opening (16), said infeed unit suitably being provided with a counter means. In conjunction therewith, the associated infeed and packing means of the cassette are inserted into the unit, whereupon banknotes can be fed into the cassette. The cassette, with the banknotes therein, is then released from the infeed unit while closing the infeed opening, whereafter the cassette is transported to a collecting location, e.g.