The Taxation Law in Indonesia refers to Self-Assessment System, which is giving trust to the taxpayer to calculate, deposit and report by themselves about the amount of tax owed according to the regulation of taxation law. While the purpose of writing this thesis generally is to know about the imposition, deposit and reporting of value-added tax by PT. Seimitsu Diagnostics has appropriated with the provision of value added tax law within the applicable taxation enforcement rules and to know how PT. Seimitsu Diagnostics to overcome the obstacle encountered in implementing the value-added tax collection and to know the  effort that have been taken to overcome the problems. The writer does this research by collecting data and processing method and analysing data. The writer does the research in the company to get the data and collecting them. The obstacle is about the output tax difference always bigger than the input tax, so it can cause there are the amount of underpaid taxes and the company is considered to be negligence in the deposit and report the underpaid taxes on every tax period or tax year so according to article 8 section (2) Law number 6 Year 1983 about the General Condition and tax procedure of the company got penalty to a 2% interest in a month for the underpayment amount.

This study aims to examine the effect of Gross Profit Margin, Net Profit Margin and Cash Turnover on Return On Investment in Manufacturing companies listed on the Indonesia Stock Exchange in 2015-2019. The source of data in this study is secondary data in the form of financial statements of manufacturing companies listed on the Indonesia Stock Exchange. The data collection technique for this research is data accessed through the website www.idx.co.id. The results of this study indicate that partially based on the T test gross profit margin, net profit margin and cash turnover have a positive and significant effect on return on investment. Simultaneously based on the F test gross profit margin, net profit margin and cash turnover simultaneously affect the return on investment. Based on the results of the analysis of the correlation coefficient and the coefficient of determination shows that the relationship between gross profit margin, net profit margin, cash turnover and return on investment is very strong and most of the return on investment is influenced by the three independent variables.

Pembangunan Nasional adalah kegiatan yang berlangsung terus-menerus dan berkesinambungan yang bertujuan untuk meningkatkan kesejahteraan rakyat baik materil maupun spiritual. Untuk dapat merealisasikan tujuan tersebut perlu banyak memperhatikan masalah pembiayaan pembangunan. Pembiayaan pembangunan utamanya digali dari sumber dana yang berasal dari dalam negeri di antaranya berasal dari penjualan minyak dan gas bumi (migas), pajak, dan sumber daya alam lainnya yang kesemuanya diatur dalam Anggaran Pendapatan dan Belanja Negara (APBN). Dalam APBN terlihat bahwa pajak merupakan sektor penerimaan terbesar dalam hal pendapatan negara yang mencapai 75% dari seluruh jumlah penerimaan negara. Tujuan dari penulisan penelitian ini adalah untuk mengetahui apakah penghitungan, pembayaran dan pelaporan PPh Pasal 25/29 oleh PT. Aneka Gas Industri telah sesuai dengan ketentuan peraturan perundang-undangan perpajakan. Selain itu untuk mengetahui apa masalah dan hambatan yang terjadi dalam pelaksanaan kewajiban perpajakan PPh Pasal 25/29 serta upaya perusahaan dalam mengatasi masalah tersebut. Metode pengolahan data yang digunakan dalam penelitian ini adalah metode deskriptif analitis yaitu penelitan yang dilakukan berdasarkan pengumpulan data dan analisis data yang telah diperoleh selama mengadakan penelitian.