Mortgage bankers that trade in the to-be-announced MBS market will be exempt from the initial margin requirements associated with the Financial Industry Regulatory Authority’s revised Rule 4210, which was approved by an order of the Securities and Exchange Commission last week. Under the rule, as amended now three times by FINRA, market participants who trade TBAs will have to post an initial “maintenance” margin of 2 percent of net position size, along with an on-going variation margin, which will be subject to a $250,000 minimum transfer amount. However, the SEC order provided...