Introduction: Today, since hospitals and clinics are facing the challenge of resource shortages and rising costs, the information and cost of health services can be useful in dealing with optimal resource allocation, identifying the level of performance of activity centers on the use of resources, reforming the budget and tariff rates. This study aims to calculate the cost of service at the laboratory department of Alami Herandi Clinic (Isfahan Social Security Organization) and comparing it with the approved tariffs in 2015.Method: In terms of objective, this study uses the practical- developmental method and in terms of nature, it is based on survey research, and the survey data has been collected using a combination of library and field methods, including note-taking, open interview and observation. The cost of service for 51 types of tests, which are done at the laboratory department of Alami Herandi Clinic (Isfahan Social Security Organization) in 2015, was calculated using time-driven activity based costing. First, the activity centers are defined and divided according to operation and support. After calculating the costs of support centers and allocating them to operation centers and adding the total amount to the direct costs of the laboratory, the total cost of this department is calculated. Then the service cost of each unit is calculated suing time- driven activity based casting (TDABC) and finally, it is compared with the approved tariff rates of 2015. Finally, the difference between the mean of cost and the mean of tariff rates was analyzed by paired sample t-test.