Registering for the Goods and Services Tax (GST) is a major milestone for any growing Singaporean SME. The Inland Revenue Authority of Singapore (IRAS) actually provides a valuable concession: the ability to reclaim pre-registration GST. Here is how to legally execute a pre-registration GST claim. You can only claim input tax on services if they were incurred within 6 months prior to your official GST registration date. A botched pre-registration claim often triggers an immediate IRAS review and potential penalties.