Income taxes are imposed on a Foreign Corporation in the amounts that each of the following items prescribes for the category to which the item refers:
外国法人に対して課する所得税の額は、次の各号の区分に応じ当該各号に定める金額とする。
domestic source income as prescribed in the preceding Article (other than what is set forth in the following item and item (iii)):the amount calculated when that domestic source income (or the amount prescribed in Article 169, item (ii), item (iv), and item (v) (Income Tax Base for Separate Taxation), for domestic source income as set forth in those provisions) is multiplied by a tax rate of 20 percent;
domestic source income as set forth in Article 161, paragraph (1), item (v) (Domestic Source Income): the amount calculated when that domestic source income is multiplied by a tax rate of ten percent;
第百六十一条第一項第五号（国内源泉所得）に掲げる国内源泉所得 その金額に百分の十の税率を乗じて計算した金額
domestic source income as set forth in Article 161, paragraph (1), item (viii) and item (xv): the amount calculated when that domestic source income (or the amount prescribed in Article 169, item (i), for domestic source income as set forth in that item) is multiplied by a tax rate of 15 percent.
第百六十一条第一項第八号及び第十五号に掲げる国内源泉所得 その金額（第百六十九条第一号に掲げる国内源泉所得については、同号に定める金額）に百分の十五の税率を乗じて計算した金額
定義第百六十一条第一項・この編の中だけ
次に掲げるもの
わかりやすく言うと
非居住者と法人の納税義務を定める編で、日本国内に源泉がある所得として列挙されたものです。国内の恒久的施設に帰せられる所得、国内にある資産の運用や譲渡による所得、国内での勤務による給与、国内の営業所に預けた預貯金の利子などが挙げられています。