The purpose of this study is to examine and analyze the effect of service quality and effectiveness of supervision on corporate taxpayer compliance, testing and analyzing competence can moderate the relationship between service quality and effectiveness of supervision with corporate taxpayer compliance at Medan Polonia Tax Office, Medan City. In collecting data, this study distributed questionnaires to 99 respondents registered at KPP Pratam Medan Polonia in 2017 through probability sampling. Data analysis techniques using multiple regression (multiple regresion analysis) and residual tests using the concept of lack of fit. The results found: first, the quality of account representative services has a positive and significant impact on corporate taxpayer compliance; secondly, the effectiveness of account representative oversight has a positive and significant effect on corporate taxpayer compliance; third, the quality of account representative services and the effectiveness of account representative oversight has a significant (real) effect on corporate taxpayer compliance; and fourth, account representative competencies do not moderate the relationship between the quality of account representative services and the effectiveness of account representative oversight of corporate taxpayer compliance Abstrak: Tujuan penelitian ini adalah untuk menguji dan menganalisis pengaruh kualitas pelayanan dan efektivitas pengawasan terhadap kepatuhan wajib pajak badan, menguji dan menganalisis kompetensi dapat memoderasi hubungan antara kualitas pelayanan dan efektivitas pengawasan dengan kepatuhan wajib pajak badan pada Kantor Pelayanan Pajak Medan Polonia, Kota Medan. Dalam pengumpulan data penelitian ini menyebarkan angket kepada 99 responden yang terdapaftar di KPP Pratam Medan Polonia Tahun 2017 melalui probability sampling. Teknik analisis data menggunakan regresi berganda (multiple regresion analysis) dan uji residual menggunakan konsep lack of fit. Hasil penelitian menemukan: pertama, kualitas pelayanan account representative memiliki pengaruh positif dan signifikan terhadap kepatuhan wajib pajak badan; kedua, efektivitas pengawasan account representative berpengaruh positif dan signifikan terhadap kepatuhan wajib pajak badan; ketiga, kualitas pelayanan account representative dan efektivitas pengawasan account representative berpegaruh signifikan (nyata) terhadap kepatuhan wajib pajak badan; dan keempat, kompetensi account representative tidak memoderasi hubungan antara kualitas pelayanan account representative dan efektivitas pengawasan account representative terhadap kepatuhan wajib pajak badan.