You are right and that system is already operational in India. This is a major shift from the old system and also entails lower margin blocking. Let us take the case of one of the exchanges running into a technical glitch. In such a case, you need to wait for the glitch to be resolved or if you want to trade in the other exchange you need to have sufficient margins in that clearing corporation without which you cannot take positions. This becomes a challenge since most traders run a tight ship and will not have sparer margins of that order.

When there is a trading halt, it is the task of the brokers to ensure that trades are carried out on behalf of clients. In the current situation, brokers would be unable to square off open positions (client and proprietary) resulting in high losses. This job becomes easier when there is interoperability because it can resolve the issue as it can allow the margin/ fund usage across clearing corporations. That means your margins with the NSE Clearing Corporation can be used for clearing trades executed on the BSE and vice versa. Effectively you don’t need to pay dual margins to square off your position in another exchange.