SoftBank Group has also been found to have made miscalculations related to foreign exchange losses and logged some costs in the wrong period.
Following the miscalculations and errors being pointed out by tax authorities, SoftBank Group was made to re-file its taxes.
In a statement made by the Japanese multinational conglomerate, it said it had amended the errors at the request of the Tokyo Regional Taxation Bureau.
SoftBank Corp., the group's major mobile phone carrier, was also found to have under-reported income resulting in a back tax surpassing 1 billion yen (9.42 million U.S. dollars).
SoftBank Corp. said it had also re-filed its amended income with tax authorities.
Previously, in the business year through March 2018, SoftBank Group was found to have failed to declare about 400 billion yen (3.77 billion U.S. dollars) in taxable income.