The development of credit and debit cards and the invisible information which they hold raises an argument that these cards may not be covered by the meaning of “document” in the context of forgery under the Libyan Penal Code. Under forgery law in Libya, the subject matter of forgery must be a “document” or a “paper”. Because the principle of legality is one of the legal systems’ fundamental principles, these two words (document and paper) may not be applicable to credit and debit cards. This raises a problem not only relating to whether existing criminal law covers the alteration of information on credit and debit cards, it has also features when one considers whether current Libyan law provides for an offence of using one of these false cards. The offence of using a forged document requires a forged document as a subject matter of the offence. Thus, existing forgery law under the Libyan Penal Code may not be applicable to credit and debit card forgery. Another problem which occurs is that possession under the Libyan forgery law is not a crime. Therefore, the possession of a false credit or debit card is not currently an offence in Libya. This raises another problem which confirms the insufficiency of the current forgery law in Libya. Therefore, this thesis begins by examining the concept of credit and debit cards and the information they contain. Thereafter, the subject matter of forgery under the Libyan Penal Code, namely the words “document” and “paper” will be explored, followed by an examination of the offence of using a false credit and debit card, and the potential offence of possession. The main aim of the thesis is to suggest an effective proposal to the legislator in Libya for improving forgery law to deal with credit and debit card forgery.