My Home Return Permit 港澳居民來往內地通行證 is expiring in May. How can I renew it in Sydney?

You can go to the consulate in Sydney to try to ask for the issuance of a new Home Return Permit. If it can't be done, you can apply for a Travel Document of the PRC, which allows you to enter mainland. You need to submit a filled application form, two bareheaded photos against white background, and the original and photocopy of your HK passport. The normal process takes four working days.