How can i link expenses/job costs to a job that will show up on the custom report profit and loss by customer?

Hi there, 

Welcome to the Community. I'll be glad to share more info and steer you in the right direction so you can continue to navigate the program with confidence. 

Based on what you've described, I see you benefiting by using the Projects feature offered in the program. When it comes to tracking individual jobs or projects, I suggest using the Projects feature. Feel free to learn more about Projects using this link here. In order to learn more about how people use Classes and Locations, I encourage you to check out this helpful article here as it provides more in-depth info. This way you can track the transactions on your Profit and Loss report. 

Let me know if this info helps. You're more than welcome to ask other questions. I'll be here.