The study aims to determine the income tax calculation procedure of Article 21 In SMP St. Tarcisius Dumai The research method of data by conducting interviews, observation and data collection of primary, junior secondary at St. Tarcisius Dumai "Analysis Calculation of Income Tax Article 21 on the SMP St. Tarcisius Dumai". Results of the study found that SMP St. Tarcisius Dumai wrong in calcul…