That's all you have to do - register for tax and/or VAT.
If you're doing business under a name that's not your own personal name, you should register a business name with the CRO. Simple and fast.
Also, you'll want a seperate bank account for your business transactions. The bank will require you to have proof of a registered business name before they'll accept a cheque made out to Joe Bloggs Consulting, for example.
But if you're doing business simply under your own name, all you need is the tax registration.