Select Project at Transaction Entry Whenever you record a transaction (Journal Voucher, Payment Voucher, Sales Invoice, etc.), you must select the relevant Project from the project field.

• System auto-updates reports: income and expenses flow into that project’s P&L.
• Clear visibility: You instantly see profit or loss per project.
• To see the project wise profit and loss statement, go to the project module and select reports.

In short: Select the project at transaction entry, and the system will automatically show project-wise profitability in reports.

https://www.youtube.com/watch?v=vkJTGyspdwg