The purpose of granting an extension of time is to fix the period by which the date of completion should be extended, depending on the incidence of the events concerned and measured by what is fair and reasonable provided the contractor submit a notice of delay to apply for the extension. This study aims to advocate the contractor in minimizing mistakes frequently committed during extension of time application. Quantitative research approach using survey form among architects registered with Malaysia Institute of Architects member list with office located in Kuala Lumpur was adopted. Data collected revealed that failure to issue notice of delay which caused outright rejected was the main common mistakes. This study concluded that to minimize the common mistakes that contractor frequently committed during submission, contractor must be equipped with good contractual knowledge and good record keeping practice