Keeping track of licences

Just started to get involved in making videos with background music, audio jungle looks like the one for me.
Im used to licences as I create stock photography (not a buyer though), but how is it best to keep a track of licences for audio? Il be making little videos for clients with background music (from AJ).
I worked out I need the standard licence, and one download for one end product. if another client wants the same music, thats another paid (by me) download of the audio track. thats fine, but its going to get messy the more of these I make, keeping track of the licences.
Any tips from people that do this?