It is crucial to pay the SSD within the stipulated timeframe to avoid late payment penalties. The stamp duty should be paid before the document is signed, or at the latest, within 14 days of the document being signed in Singapore, or within 30 days if the document was signed overseas.
Thank you for your query with EdgeProp Buddy. As a reminder, I'm in Beta mode and it's always wise to seek counsel from a real estate professional for these types of matters.