With "Treasury Style" Clearing and Reporting, your FX trades are decomposed in their respective single currency components.
We report the currencies positions that result from your trades - e.g. if you Bought 100K of EURCHF @ 1.5700, we will report a Long position of 100K in EUR and a Short position of 157K in CHF for the appropriate value date of the trade.
In Treasury Style accounts, Marking to Market is operated by calculating the USD conversion value of each of your Currency Positions.
All open Currency Positions in excess of $10,000 (unless otherwise agreed with you) coming to maturity, will be rolled to Spot value date against US Dollars through a TN or ON Swap.
Currency Positions below this threshold will be allowed to go to maturity and delivered to your cash accounts. An automatic conversion of these multi currency cash amounts to your CAC can be agreed.