Whenever you sell securities, the stocks are earmarked for delivery to the clearing corporation on the very same day. These sold shares are then debited from your demat account on the settlement days i.e., on T+2 days. The DP charges are taken on the day when the stock is earmarked for delivery.
If shares are sold partially from your demat account and partially via a BTST transaction, then the DP charges are collected twice since the stock is separately earmarked and debited from your account
Let’s understand this with an example.
You have 50 shares of TATA Motors in your demat account. On a Monday, you buy more 50 shares of TATA Motors. On the next day, you decide to sell off all 100 shares of TATA Motors. The 50 shares that were already in your demat account will get earmarked for delivery by Tuesday evening, and that’s how DP will be charged.
On Wednesday (according to the T+2 norm), the additional 50 shares bought on Monday will turn up in your demat account and quickly be earmarked for delivery. Therefore, the DP will be charged twice for these 50 shares.
On Thursday, which is the settlement day for the sale that happened on Tuesday, two debit transactions reflected in your account, one for the first 50 shares and second the 50 shares that were bought later. As there are two individual incidents of earmarking and debit of the stock from the demat account, the DP will also be charged twice.