In order to ensure rollovers do not affect clients, a cash adjustment needs to be made.
This is explained in the following examples:
Let’s say the SPI for March closes at 5050/5051 and SPI for June opens at 5000/5001.
Example 1: You buy 10 contracts
If your position is a Buy, it closes on the old Bid price of 5050 and reopens on the new Ask price of 5001. Because you are in a Buy and the new market price has decreased, your open trade P&L has made a loss. As a result, you will receive a positive adjustment amount in your swap column equal to the difference between the old Bid and the new Ask.
You will receive (5050-5001)*10 contracts = $490 AUD
Example 2: You sell 10 contracts
If your position is a Sell, it closes on the old Ask price of 5051 and reopens on the new Bid price of 5000. Because you are in a Sell and the new market price has decreased, your open trade P& L has made a gain. As a result, you will receive a negative adjustment amount in your swap column equal to the difference between the old Ask and the new Bid.
You will receive (5051-5000)*10 contracts = -$510 AUD