Incentives received by employees

A Query:

A company is paying  incentives in FY 2012-13 (including some incentives for FY 2011-12) to some of its employees based on their performance. The Company is not paying incentives on monthly basis or not on fixed basis.

Whether this Incentives should be taken into those Employees' Salary to compute TDS on Salary (sec. 192) by the Employer (Company)?

Please suggest.