''Standing Order'' in Chinese?
The most literal translation is 常行指示 ('standing instruction'). It is seen used in HSBC and Standard Charted documents. BOC uses 常設指示, which is similar.
定期/按期 (regular; periodical) + 付款/支付 (payment) are also possible, perhaps more idiomatic, translations of standing order in banking (see here), but they are not literal. They also do not specify if the regular payment is pre-instructed by a bank account holder.