Please advise how to extract P&L department wise ?

Welcome to the Community, @ritu-fgpro. 

It feels great to see your first post today. I've got some easy steps for you to pull up a Profit and Loss by Department report. This way, you can get detailed information on your income and expenses by department. 

Here's how:

1. Go to the Reports menu, then enter Profit and Loss by Department in the Search field.
2. Click the Customize button to add additional customizations to the report.
3. Update the Report period, then click Run report. 
4. Select the Filter menu, then mark the Department box and select the department you want to view on the report.
5. Click Run report.

To learn more about customizing your Profit and Loss report in QBO, read through this article: Customise reports in QuickBooks Online.

I'm always around here to help you more should you have follow-up questions about running reports. Take care.