Marcel, in our upcoming Q3 release of the new supplier management product, there will be a 'prevent duplicates and merge' function. Currently, there is no way to automate the tagging or prevention of duplicates in the system. Once the new release is GA and proper integration set up, you will be able to prevent duplicates at the outset of supplier creation and search for existing duplicates in the system with the ability to merge/delete duplicate records to one master record.
Regards,
Eric Coker