If you are a new researcher (PhD students, Post-Doctors, and Professors) coming to Austria, you may be entitled to the immigration tax benefits, which reduces your tax rates by 30%.
Please check the URL: https://www.euraxess.at/austria/information-assistance/taxation-and-salaries
More information can be found by searching "Zuzugsbegünstigungsverordnung".
Perhaps, the Ph.D. students can be also qualified for this tax policy because the check-list of new Ph.D. students in TU Graz mentioned this regulation.
"Check whether you are entitled to a favourable tax treatment for highly qualified researchers (Zuzugsbegünstigungsverordnung) by the Austrian Federal Ministry of Finance. For further information and advice, please consult a professional tax advisor."
Important: please note that you can only apply for this benefit within the first 6 months after moving into Austria.
Please also consult other colleagues, who have applied for it successfully before.
Good luck with your application.