Reason: Tax calculator will work based on the information available in the Payroll system.(i.e Income Tax computation sheet). If the IT Statement is not released for the latest month then you may get the message that the "Tax info not available".
Solution : You will have to release the IT Statement for the latest created month. You will be able to find this option under "Payroll--> Payroll Central" select the latest month and Release IT statement. Once the above said process is complete the employee will be able to use the Income tax Calculator