Thermo-luminescent Dosimeter (TLD) is very effectively used for personnel monitoring at Madras Atomic Power Station since criticality of the first Unit. The TL Phosphor in use is CaS0₄ : Dy. The period for personnel monitoring is selected as Service month. Sufficient number of control TLDs are used and control readings are always referred for dose estimation. In certain cases control reading plays an important role in evaluating the individual dose as well as collective dose during dose estimation by TLD. Two different cases of interest for individual dose and one scenario for collective dose are identified for detailed analysis. The role of control reading in the estimation of individual and collective dose and methods for correction on control reading to improve the accuracy in dose estimation are discussed in this report.