You should keep sufficient records of your business to enable the assessable profits to be readily ascertained. Know more details from here.
You are required to notify the Inland Revenue Department (IRD) of any change of postal address within one month of the event. Know how to notify IRD here.
If you are liable to tax in Hong Kong, you have to inform the Inland Revenue Department (IRD). Learn how to notify IRD of chargeability here.