Sorry, Have checked the below colleges, they do not offer the Diploma in taxation law, is their another name.?
1.I have checked the website of the Indian Law Institute, New-Delhi, it does not offer DITL.(http://www.ili.ac.in/prospec.pdf)(http://www.ili.ac.in/courses.pdf)
2.The school of law, IGNOU website also does not offer a diploma in taxation law
3.National Intellectual property Organisation, No:1, Punchkuich Road, New Delhi - 110055
This offers dipolma in Intellectual property rights and NOT diploma in taxation law.
4.Indian Institute of Patents and Trademarks, G-85, Preet Vihar, Main Vikas Marg, New Delhi- 110092. This also offers Diploma in intellectual property rights,
5.Global Institute of Intellectual Property, New Delhi also does not offer taxation courses(http://www.giipinfo.com/graduate_Programs.aspx)
6.National Law University, Delhi. also does not have a taxation law course.(http://nludelhi.ac.in/adm-pg.aspx)