Hello @shuang57,

1. Account Groups identify which accounts on the COA can be connected to projects and will require a project and task when used in a transaction. Account group causes the system to never allow a project in some accounts and to always require a project in other accounts.Account groups also allow for easy grouping/subtotaling by type of account on reports, similar to the way Account Classes group accounts on the Balance Sheet & Income STatement.
2. Acumatica has labor cost rates and labor revenue rates. There are multiple ways to set up each. For example exact labor transactions could come from the Payroll module or your Payroll ISV, or you could record payroll cost to the project using estimated labor cost rates. I recommend you work with your partner or CPA and she will guide you to the best way your labor should be set up, to correctly capture both costs and revenues.
3. I suggest you and your partner create a test environment and test through setting up your projects so you can see the impact on the test GL. Post transactions, including timecards and AP Bills, etc., to your projects and then process project billing.  Look at the transactions that posted to GL after releasing timecard and after releasing Invoices. Adjust your settings as needed to record a proper bill and proper costs in GL.   If your employee’s time is not billable then $0 revenue is on the customer’s bill, but the cost of labor will still post if you’ve configured everything properly.

Laura