A bank transfer slip needs formal Chinese number characters and your details, written by hand, often with no wifi. Learn that small fixed set from memory and the slip stops being scary.
Living in Shanghai for years and freezing on a handwritten bank slip is not a failure, it is character amnesia from typing. The slip needs a small fixed set you can relearn fast.
Chinese bank and legal forms use formal numerals like 壹貳叄, not 一二三. Here is the full set, why they exist, and how to practice writing them from memory.