As a general rule, you will be required to pay German tax if you live and work here for more than six months. The tax due is deducted from your salary immediately and transferred to the tax authorities by your employer as so-called wage tax ("Lohnsteuer"). The rate of income tax will depend on how much you earn, whether you have any dependents and which tax class applies to you. 

Germany has dual taxation agreements in place with many countries to ensure that you are not required also to pay tax in your home country. Some of these agreements also determine how you are taxed as a researcher.  The HR department or local tax authority will know which regulation applies to you. 

At the end of each calendar year you may apply to the local tax office (“Finanzamt”) to have your income tax assessed ("Einkommensteuererklärung"). This may entitle you to a partial reimbursement of tax paid. The necessary documents can be obtained from the local tax authority or online, respectively, through the tax authority’s website “ELSTER”. Often, it is worth paying a tax accountant to help you complete your tax return. 

Good to know: Church Tax 
In Germany, churches (Protestant, Catholic, Jewish) can collect taxes from their members. This is called the Church Tax (“Kirchensteuer”). In Baden-Württemberg, the Church Tax is 8% of what is withheld in income tax.  It is collected the same way as the regular wage tax and channeled through the tax authorities to the respective denominations.  

When you move to Germany, you have to register with the local citizens’ office (“Bürgeramt”). During this process, you will be asked to declare your religious status. If you do not wish to pay German Church Tax, then you should not declare any religious denomination. If you do so, there is also the option to reverse this decision and “leave” the church (“Kirchenaustritt”), again through the citizens’ office. If you are not a registered church member, however, you will not have access to certain sacraments in a German church such as getting married, baptizing a child or have a religious funeral. Other restrictions include the possibility to participate in confirmation, work in the church, its schools or hospitals, as well as becoming a godparent or to take part in parish activities in Germany.