Every German citizen has an individual tax identification number, also abbreviated as tax ID or in the tax assessment as IdNr. The tax ID has been around since 2008 and is intended to replace the tax number in the long term.
All of a person’s important data is stored under the tax ID. You must provide the number in all communications and applications to the authorities. Employers or social benefit providers such as health insurance companies use the number to transmit important tax data to the tax authorities. Since 2023, employers are only allowed to send the electronic wage tax certificate to the responsible tax office by stating the employee's tax ID, explains the tax administration of North Rhine-Westphalia. Anyone who gets married or becomes self-employed also receives a new tax number. If you get a new number, the tax office needs to assign it to you. The number can change after a tax move, so you can change your tax number after a move. You also need the number sequence for an exemption application. Investment income can be allocated to individual people and it will be noticed more quickly if the allowance of 1,000 euros is exceeded.