SSD is counted from date of TOP or date of purchase for sub sale unit?

[xtreme_46]

let say a seller want to sub sale his unit he bought in 2011 and TOP in 2013..so if now in 2012 he sell his unit..does he need to pay SSD of 16% for 1 st year? SSD is counted from date of purchase or from TOP date?

[leesg123]

Date of purchase

[buttercarp]

Start date is when you sign the S&P.