MY H1B case got approved and due to account change in IBM i need to go for amendment.

MY H1B case got approved and due to account change in IBM i need to go for amendment.How much time will it take for the process and what is the END date for filing amendment.

Amendment could take few months to process. You can check the processing time online for I-824. There is no end date to file amendment but should be filed before you start working at the new location.