In case of eMargin, the pledge validation link comes before you place the buy order. Elsewhere. the validation link for margin shares purchased today is sent to you via SMS/Email by CDSL after market hours. You must note that the pledge process needs to be completed only in cases where your margin trades are partially executed, or partial quantity is sold under MTF or CNC. The time limit for pledging is till 10:00 a.m. on the Settlement Day means T+1 / T+2 depending on the settlement cycle of the scrip.