https://www.iras.gov.sg/taxes/withholding-tax/withholding-tax-filing/withholding-tax-filing-and-payment-due-date
IRAS | Withholding Tax (WHT) filing and payment due date
Payer must file and pay WHT by 15th of second month from the date of payment to the non-resident
payment due datewithholding taxiraswhtfiling