how are others tracking inventory left on site of a commercial bldg?

New Contributor

Hello , as a commercial Hvac company we have buildings that we leave filter inventory on site,  we are wondering what other companies are doing to track what is on site and what needs to be sent before a quarterly maitinence service is being done. We need to know what is needed on site and what is on hand.  At the moment I just have them written in the notes and edit when our tech has finished and sent me a count of what is still on site.  Any suggestion on what else can be done?