Citigroup (C.N) is planning to shift the head office of its European retail banking operation to Dublin from London to benefit from lower costs and capital requirements. This week the bank wrote to clients to say the UK-based business, Citibank International Limited, which operates a small number of branches across some 20 European countries, would be taken over by Dublin-based Citibank Europe Plc. “From a strategic perspective for Citi, moving to a single pan-European bank is expected to reduce operational and regulatory complexity, capital requirements and cost,” the company told clients.