Domi Hi Domi, and welcome on Together!
You can't change the IBAN of a sub-account, but you can close your NL sub-account and open a DE sub-account with a German IBAN. If you're living in Germany, new sub-accounts will have a DE IBAN by default. Just go to: Home > More > Add sub-acccount > Account. If you're not living in Germany, go to: Home > More > Add sub-account > Local IBAN.
