It refers to assisting mainland customers to handle cross-border financial business or witnessing the signing of relevant documents in cities such as Guangdong-Hong Kong-Macao Greater Bay Area, Hongkong, China and Macau, China with local branches or institutions as witnesses. These witnesses are branches or representative offices of banks or other financial institutions. After verifying the customer's identity and signature, they witness the relevant documents to ensure their validity and legality. These documents may involve cross-border investment, trade, asset transfer and other financial business. Under the witness of Greater Bay Area Branch, customers can complete cross-border financial business or sign relevant documents with the assistance of local banks or institutions without going to financial institutions or representative offices in Hong Kong and Macao in person.