It is recommended that the amount be written vertically and that the formal Chinese characters are used to write the numbers one (壱), two (弐), three (参), one thousand (阡), and ten thousand (萬).
但し、壱（1）・弐（2）・参（3）・阡（千）・萬（万）の5つの漢字はこれら旧漢字を使い、縦書きで書くとよい。