The present invention relates to a method of processing a data record for finding a counterpart in a reference data set. In the data record a value of a data field is determined, where the data field represents an identifier. At least one synonym candidate for the value of the data field is determined from a set of predetermined identifier values. It is determined if a synonym candidate and the value of the data field fulfill a predetermined synonym acceptance criterion, and if the predetermined synonym acceptance criterion is fulfilled, the value of the data field and the synonym candidate are associated as synonyms. Thereafter a search for a counterpart for the data record is conducted by comparing to entries of the reference data set the value of the data field and/or a synonym associated with the value of the data field.