The GST is a tax on domestic consumption. The tax is paid when money is spent on goods or services, including imports. It is a tax on the value added at every stage of the production and distribution chain.
We do not have a multi-tier GST system or exempt basic necessities, because such a system benefits the better off more as they spend more, including on basic necessities. Such a system will also require a lot of resources to operate.
Instead, we have a different, but fairer and more effective system. We collect GST from all taxpayers, including the higher-income households who spend more, foreigners residing in Singapore and tourists. We then directly help the lower- and middle-income Singaporean households and seniors who pay GST for their expenses, through the permanent GST Voucher scheme and other subsidies/schemes. This approach is fairer and more effective, rather than waiving GST for some goods for everyone, whether rich or poor.