Is SSD based on OTP signed date or completion date

In Singapore, the Seller's Stamp Duty (SSD) is calculated based on the date when the Option to Purchase (OTP) or the Sale and Purchase (S&P) agreement is exercised, not the completion date of the sale. The holding period for SSD starts from the date the OTP or S&P agreement is signed and exercised, and it ends when the same type of agreement is signed and exercised for the sale of the property. This means that the SSD duration is determined from the OTP/S&P agreement exercise date of the purchase to the OTP/S&P agreement exercise date of the sale.