A goods and sales tax (GST) of 6% is levied on most goods and services in Malaysia. If you spend in excess of RM300 at any one government-approved outlet, it is possible for international visitors to claim a refund of GST on certain goods they are taking out of the country. Full details of how to do this can be found at http://gst.customs.gov.my.
There are some exemptions on GST (mainly for fresh and essential foods) but generally you’ll now find this tax added to most things you buy including restaurant meals and souvenirs. Some establishments, if their turnover is low or if they have decided to absorb the GST into their regular prices (often the case at cheaper hotels and hostels), will not add the tax on top of the bill – it’s always worth checking in advance if you’re unsure.