The tax identification number (Tax ID) and the tax number serve different purposes. The Tax ID is a unique, lifelong personal number assigned to every person registered in Germany. It remains unchanged even if you move or switch tax offices and is used for general tax identification purposes.

As a model or influencer, you primarily use the tax identification number for personal tax identification purposes when dealing with government agencies. It is required, for example, for:
your income tax return
communication with the tax office
when agencies or production companies need to verify your tax identity
certain international tax forms
It is therefore mainly used to uniquely identify you as a taxpayer.
For invoices or your self-employment, however, you generally use the tax number, as this is linked to your specific tax file at the tax office. It can change, for example, if you move or a different tax office becomes responsible for you. Self-employed individuals and businesses in particular use the tax number on invoices and in communication with the tax office.