UK Tax number not accepted by Elster

[random_wire]

Hi there !

Just came here to ask for assistance,

UK sole trader here and I earn money from Germany

I am trying to fill out the form ''Registration of the tax deduction according to § 50a EStG (from 2014)''

When asked for my tax number, I add my UK tax number here and Elster tells me that it is not a valid tax number

Grateful for any advice

Thanks in advance !!

[L. E. Fant]

Is it the form Anmeldung über den Steuerabzug zur Sicherung des Steueranspruchs bei einer beschränkt steuerpflichtigen Person?

As far as I understand this, your german customer has to pay you your royalty after deduction of tax. Her then declares this to his Finanzamt, with his german tax number.