Forging or altering bills is a fraud, should criminal responsibility be investigated?

That's right. According to national laws, forging or altering bills is a fraud, which constitutes a crime and should be investigated for criminal responsibility. The concept of negotiable instrument can be divided into broad and narrow sense. Bills in a broad sense include all kinds of securities and vouchers, such as stocks, corporate bonds, invoices, bills of lading and so on. In a narrow sense, bills are "bills" stipulated in China's Bill Law.