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does fidor allow customers from outside of germany?
As the FAQ says: yes if you live in a country from the EU, EEE, or EFTA
Read the page, it says RT1 participants, so it's supposed to be YES
RT1 is an instant payment system for real-time payments in € under the SEPA Instant Credit Transfer scheme.
https://en.wikipedia.org/wiki/EBA_Clearing#RT1