How to add an additional line level detail with amount in AR Invoice using Billing rule?

I’ve done something similar, but via the Allocation rule since you are able to use prior allocation steps as the source for the current line.  The issue with doing it that way is that you typically end up with one markup line per original source transaction, though there are some options to aggregate on the Allocation Settings tab.
 

How to apply administrative fees on a progress billing project | Community

Hey ​@meganfriesen37 , I tried this out, but not getting the required results.

I have TM billing rule defined. So an employee would record their time which would then created allocation PM transaction for task - Employee Fees.

And the admin fee is also getting calculated at the PM tran allocation level but it is not getting allocated to AdminFee task. Instead it is getting allocated to Employee Fees task, but the amount to be calculated is correct.

And then when I go ahead to run project billing it is not taking into account the admin fee line.

For this project I have created a task -- assigned an allocation & billing rule same as that of Employee Fees and rest of the tasks. I havent defined anything under Revenue & Cost budgets for this Admin Fee task.

I just want to bring in the Admin Fee project task on the invoice, which is missing.

In your allocation rule when you’re generating the admin fees, are you replacing the task ID?
 

In your billing rule on the Admin Fee Task is the billing rule picking up the account group where the admin fee is allocated/calculated?  Is it sitting in a different account group than your other pending billing?