Hi. I am from romania too and can help you with information if you want. But shortly yes you need to declare them. At the end of a fiscal year you need ask from trading 212 for the annualized report where it should tell how much profit you made in the last year( price for sell- price for buy). on this amount you need to pay 10% tax at ANAF if the profi is less than 12 minimum salaries or 20% if it is more.