Tax registration for German suppliers having only a "Steuernummer", (no VAT ID)

Summary:

German Suppliers typically have a VAT ID that gets validated upon supplier creation, so far so good.

Smaller suppliers, however, may not have a VAT ID, only a Tax Identification number called "Steuernummer" in the format 123/4567/8901. When trying to create a supplier with only the Steuernummer system will throw a validation error because it is expecting a VAT ID.

How can we allow both types of supplier tax registrations, VAT ID as well as "Steuernummer", without giving up the validation on the VAT ID?

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