47. Do political parties have to report regularly on their finances?

Source: 
政治資金規正法, 1948 (2022改正)
Political Funds Control Act, 1948 (as amended by Act No.68 of 2022)

第十二条　政治団体の会計責任者は、毎年十二月三十一日現在で、当該政治団体に係るその年における収入、支出その他の事項で次に掲げるものを記載した報告書を、その日の翌日から三月以内に、第六条第一項各号の区分に応じ当該各号に掲げる都道府県の選挙管理委員会又は総務大臣に提出しなければならない。

Article 12. The accounting officer of a political organization shall, within three months from the day following December 31 of each year, submit a report to the prefectural election administration commission or the Minister of Internal Affairs and Communications, as specified in the respective items of Article 6, paragraph 1, based on the classification set forth in those items. This report shall detail the organization's income, expenditures, and other matters pertaining to that year as of December 31.

The treasurer of a political party should submit a report on income and expenditures annually.