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Hello, I need some advise regarding application for EUSS for my dependent parent. I applied using app but recently I found out that I need to use paper version because I am british citizen. I came to the UK on November 2005, 2008 I received registration certificate and finally I received British citizenship (2013).
My mum joined to me on 14th of April 2024 and we made online application on 19 of May 2024. Now I know that this application will be refused. What evidence do I need for this paper version? My mum is dependent of me due to her health condition.

Because you are a British citizen, you can no longer use the EU route since Brexit. You have to apply for the Adult dependent route, which is almost impossible to get.