The invention relates to the decoding of charging data records (CDR) generated in a mobile telephone network. These records consist of files to be decoded that can be described on the basis of a formal description of the ASN.1 type. On the basis of: i) a description of the type of record to be decoded corresponding to at least a first type (GSM) and at least a second type (GPRS) of records to be decoded, and on the basis of ii) said formal description of the type ASN.1 of the records to be decoded, an interpreter of the ASN.1 type (18) self-generates an updated version of decoder (10) of at least a first and at least a second type according to the type of record to be decoded. The files to be decoded are sent to the decoder created in this way, so as to output the decoded CDR records in text format.