Does it affect the tax authorities to have a Rebellion account?
By law, if you are a Spanish resident and you have more than €50,000 in your Rebellion account on December 31, you will have to declare it in the 720 model. Currently, the maximum balance you can have in your account is €20,000.
Is Rebellion registered or "connected" to the Bank of Spain?
Rebellion is not directly connected to the Bank of Spain but it is connected to the Central Bank of Lithuania. The latter is directly connected to the Bank of Spain.