Government Regulation Number 46 Year 2013 (Government Regulation 46) concerning Pajak Penghasilan Atas Penghasilan Dari Usaha Yang Diterima Atau Diperoleh Wajib Pajak Yang Memiliki Peredaran Bruto Tertentu, is an enhancement of tax reform made to boost voluntary tax compliance. Government Regulation 46 has come into effect since July 1, 2013. The issuance is intended to simplify tax in area of MSMEs with the imposition of 1% final tax rate for gross turnover not exceeding 4,8 billion rupiah in one taxable year. The purpose of this research is to figure out taxpayers’ growth 54 months before and after implementation of Government Regulation 46, as well as the effectiveness and contribution towards Income Tax Law Article 4 paragraph (2) at KPP Pratama Medan Barat. This research uses qualitative descriptive analysis. The result of this research regarding the average taxpayers’ growth 54 months before and after implementation, shows an increasing taxpayers’ growth of 7,54%. In yearly basis, an increment happens on taxpayers registered after implementation from year 2014 to 2017. The effectiveness of Government Regulation 46 lasts in 2017 with 70,56%; with criteria of less effective. The average contribution towards Income Tax Law Article 4 paragraph (2) shows 13,87%; with below average criteria. In the upcoming timeline, government through KPP Pratama Medan Barat needs to make an improvement in seizing the potential taxpayers and to maintain satisfying performance in managing tax revenue.