The new biggest bank starts through the merger of the Bank of Tokyo-Mitsubishi and UFJ Bank. It begins business Jan. 4.

Their holding companies, Mitsubishi Tokyo Financial Group Inc. and UFJ Holdings Inc., delayed the merger of their core banking arms for three months to ensure smooth systems integration. The new bank has the largest number of, about 40 million, bank accounts in the world. The holding firms themselves, as well as their trust banking and brokerage arms, are scheduled earlier to merge Oct. 1, 2005. It makes the largest financial group in the world with total assets of more than 19 billion yen.