All businesses operating in Singapore (yes, including sole proprietorships) are required to be registered compulsorily for GST if they meet the following conditions:-
a) your taxable sales turnover for the past four quarters exceeded S$1 million or
b) you reasonably expect the next 12 months taxable turnover to be more than S$1 million
If your company meet the above conditions, please make sure you take the necessary steps to prepare for registration.
This is because IRAS have the authority to imposed penalties on the GST due from the date your business is liable for registration.
The liability for registration nowadays is easily achieved as we see more and more companies having sales turnover exceeding S$1 million. So, if your business need to be registered, please do so before the taxman comes to visit!