If spouses/partners are permanently separated in 2025, they must notify the tax office using the official form Application for income tax reduction and for income tax deduction features 2025 - main form and attachment "Tax class change". The notification can also be made electronically at My ELSTER if you are registered at ELSTER. The permanent separation will be noted in the electronic wage tax deduction features (ELStAM). Tax class I is automatically assigned for the following year (from 2026).
However, spouses/partners can apply to the tax office for a tax class change. The application is made using the form Application for income tax reduction and for income tax deduction features 2025 - main form and attachment "Tax class change", which both spouses/partners must sign. The application can also be submitted electronically at My ELSTER. Spouses can choose between the tax class combinations III/V, IV/IV or IV/IV with factor.
Each employee also has the option of having a less favorable tax class (i.e. higher wage tax deduction) noted in their ELStAM. In relation to tax class II, only tax class I is to be regarded as less favorable, in relation to tax class III, tax classes I, II and IV are to be regarded as less favorable. The form Application for wage tax reduction and for wage tax deduction features 2025 - main form and attachment "electronic wage tax deduction features" can be used for this purpose (also via My ELSTER).