https://www.scmp.com/business/compa...gibility-and-whats-big-deal-alibabas-fungible
Q: How can the transaction be executed?
Any broker licensed by the US and Hong Kong exchanges can execute the transaction.
ADS holders who intend to convert their ADSs into Hong Kong-listed shares (9988) must first turn in their ADS to the depositary bank Citibank through their brokers. Upon payment of the relevant fees, applicable taxes or charges, Citibank will deliver the corresponding number of Hong Kong shares into a Hong Kong brokerage account designated by the investor, or the broker.
Shareholders of the Hong Kong-listed stock (9988) who want to convert their holdings into ADSs in New York must deposit them with Citibank Hong Kong, the custodian bank. Upon payment of relevant fees, expenses, taxes and charges, the depositary will issue the corresponding number of ADSs for delivery to the designated account,
Alibaba said in its prospectus.