HSBC Hong Kong has started asking some existing mainland China investment clients to file a source-of-funds declaration through its app by Sept. 12 and update their contact details, extending checks that had already been applied at the new account opening stage. The form requires clients to confirm that money used for investing comes from lawful sources outside mainland China and acknowledges that personal data may be disclosed to law enforcement or regulators on request. Clients who miss the Aug. 20 deadline may see investment services suspended, while those who do not submit by Sept. 12 may have those services terminated. HSBC said the self-declaration is meant to keep information provided for know your customer and customer due diligence current and valid, and said the latest requirement applies only to investment services clients.