Tax authorities have said NTT Mobile Communications Network Inc. (NTT DoCoMo) and its group failed to properly declare a 26 billion yen-plus taxable investment in equipment for its personal handy-phone system over a one-year period beginning in April 1998, NTT DoCoMo announced Tuesday.

NTT DoCoMo and its eight regional group companies are being ordered by the Tokyo Regional Taxation Bureau to pay about 11 billion yen in additional taxes and penalties, NTT DoCoMo said in a press conference.

The company said it is considering appealing against the measure.