One of the employees have taken an unpaid leave, which I want to record in QB so that it will calculate his loss of pay from his salary. How do add the details?

Let's add your employee's unpaid leave to ensure QuickBooks Online (QBO) will calculate the pay accurately, Anamika.

You'll want to ensure first that you've added the leave category to track or manage your employees' leave. Ensure that your Unpaid Leave category is set to Not tracked under the Employee Leave Balance. Here's a screenshot for your visual reference:

   

Once done, you can now adjust the employee's pay run and add the unpaid leave line item from there. Here's how:
 

1. Go to My Apps and choose Payroll.
2. Select the Employees tab and open the pay run for the period that includes the unpaid leave.
3. Click the employee drop-down.
4. Then, select Take leave from the Actions button.
5. Enter the Unpaid leave category you've set up.
6. Tick Save once done.

From there, you'll ensure that the employee's salary is correctly adjusted to account for their unpaid leave, and the deduction is properly reflected in their pay run and your payroll records.

Feel free to reply again in this thread for more questions about managing your employees or payroll in QBO. We're here to help in any way we can, Anamika.