After getting GST registered, you need to charge GST on all taxable supplies at the prevailing GST rate excluding supplies that come under the customer accounting category. The GST charged and collected by you is known as output tax and should be paid to IRAS within one month from the end of the accounting period. As you are registered for GST, you can put a claim on the GST that you paid for your business purchases including imports and expenses and file it as input tax in your GST return. However, you must fulfil all the applicable conditions for claiming this input tax.