Is Group per Hour Billing allowed as per Income tax India ?

Hi Experts,

We are a Engineering consultancy company having a Foreign Branch and a Subsidiary (Domestic Company) in India,

Our employees are registered under Domestic Company ,

We have Projects under Foreign Branch 

So our employees who are registered under Domestic company is working for Foreign company and monthly invoice is raised to the Foreign company based on the hours spend by the employees

So we find Cost Per hour of each employee and add a margin to actual cost , later we group these employees into 7 categories and each group is assigned with a standard Cost per Hour 

Those employees who are coming under each group will be having same Cost Per hour 

Then total Hours of each Group is calculated and multiplied with standard Cost Per Hour assigned for each group

Then invoice is Raised to Foreign Branch

Is this kind of invoicing allowed under IT India

I heard PWC is having similar kind of invoicing

Thank you!