You don't need to register an ebook but I do recommend doing so. This is something your publisher can do for you (to make the whole process a lot less complicated) but it is also something you can do yourself by contacting ISBN Australia and completing the various paperwork and paying the various charges for 1) your ISBN and 2) your barcode.
The reason I recommend registering an ebook is because by doing so your ebook is protected by the same laws as your physical book. When I say protected though the protection would be good in Australia but as soon as you release your book on the world wide web the high quality free protection we have here simply by putting the copyright symbol on your book not only needs to be paid for per country (if you would like that same protection outside of Australia) but to be perfectly honest with you it will do jack-all.
If someone wants to steal or plagiarize your book they will and unfortunately there is not much you can do to stop them. As such you need to make the decision before you release your book to the general public as to whether the pro's of releasing it eg. the enjoyment, money and credibility you will receive etc. out way the cons eg. multiple people all over the world pirating or plagiarizing your book in some manner.
If you go through ISBN Australia the full process (if you have never done this before) will take approximately 2 weeks. If your publisher does it for you your registration can be approved within 72 hours. They other key difference you need to note though is if you do this for yourself you will be your own registered publisher whereas if your publisher does it for you they will be your registered publisher.
For self and online distribution this doesn’t matter but when it comes to bookstore distribution only your distributor (who needs to also be your registered publisher) will be able to put your book into bookstores for you via traditional distribution channels in other words choose your registered publisher carefully as it could be the difference as to whether you can distribute your book to bookstores down the line without needing to re-register a second edition or worse re-print that edition to display the new registration in the required positions eg. isbn + barcode on back cover, isbn + publisher’s name in the publisher’s imprint etc.
And I will let you in on another secret too. When someone does take advantage of you via either piracy or plagiarising and you decide to take legal action in regards to it (which by the way is not something I recommend but is also the only way to rectify this injustice) did you want to know how to protect your intellectual property before it is released so you can prove they copied you and not the other way around? – post it to yourself. It sounds too simple but if you print out a copy, post it to yourself and never open the envelope, the sealed envelope post marked with the date you sent it will a) quickly prove who had the content first and b) hold up in a court of law if you ever need it to.
If you would like more information on getting The Publishing Queen to register your book for you click here.
For more information on online distribution click here.