I think it will be a good idea to track payment history on client card under a new tab saying spend. because clients ask what have they paid and when they have paid and what treatment was it for. Its too much going back ward and forward trying to figure out as it is lengthy way trying to look under sales transactions etc. In our old premier spa system there was a spend tab under client card where you could see each transaction and what it was for i.e. products or treatments.