Capital income is subject to a flat rate tax of 25% for private investors. In addition to this, investors will have to pay the so-called "solidarity" surcharge of currently 5.5% on the capital gains tax, i.e. 26.375%.
The difference between the tax actually withheld, including the solidarity surcharge, and the rate that applies under the double taxation treaty is reimbursed to the shareholder by the Federal Central Tax Office (Bundeszentralamt für Steuern) upon application. Please note that the reimbursement may be subject to further conditions.