Under the law, a person (known as the payer) who makes payment(s) of a specified nature (e.g. Royalty, Interest, Technical Service Fee, etc.) to a non-resident company or individual (known as payee) is required to withhold a percentage of that payment and pay the amount withheld (called 'Withholding Tax') to IRAS.
To find out the percentage to withhold, you can refer to Types of Payment and the Applicable Withholding Tax Rates
From 1 Jul 2016, the withholding tax form can only be filed electronically via myTax Portal. The payer must e-file and pay the withholding tax to IRAS by the 15th of the second month from the date of payment to the non-resident.