The income specified by Cabinet Order prescribed in Article 161, paragraph (3) (Domestic Source Income) of the Act is to be, out of the income arising from a Nonresident's conducting a transportation business by vessel or aircraft both in Japan and outside Japan, the income that should arise from the Nonresident's operations in Japan, as determined on the basis of the revenue pertaining to passengers or cargo boarded or loaded in Japan in the case of a transportation business by vessel, and, in the case of a transportation business by aircraft, on the basis of the revenue or expenses pertaining to its operations in Japan (meaning operations conducted in Japan; the same applies hereinafter in this Article), the value of the Fixed Assets used for those operations in Japan, and other factors sufficient to estimate the degree to which those operations in Japan have contributed to the generation of income from that transportation business.
法第百六十一条第三項（国内源泉所得）に規定する政令で定める所得は、非居住者が国内及び国外にわたつて船舶又は航空機による運送の事業を行うことにより生ずる所得のうち、船舶による運送の事業にあつては国内において乗船し又は船積みをした旅客又は貨物に係る収入金額を基準とし、航空機による運送の事業にあつてはその国内業務（国内において行う業務をいう。以下この条において同じ。）に係る収入金額又は経費、その国内業務の用に供する固定資産の価額その他その国内業務が当該運送の事業に係る所得の発生に寄与した程度を推測するに足りる要因を基準として判定したその非居住者の国内業務につき生ずべき所得とする。