There is no fixed expiration dates for existing contracts and investors can hold them indefinitely, but with every passing day, investors are required to pay overnight interest. That means contracts that are not settled on the opening day and are held into the next day will produce overnight interest.
Calculating formula XAU /XAG: opening price x contract unit x number of lots x interest rate ÷ 360days x USD Exchange Rate = overnight interest
Example: Select on the trading platform Spot Gold trading and open 1 lot, with opening price is US$2300/oz., and one overnight, and LLG interest rate of -1.25% on that day.
The calculation is: opening price US$2,300/oz. x contract unit 100 oz. x number of lot 1 lot x interest rate -1.25% ÷ 360 days x USD Exchange Rate 7.8 = -HKD62.29