1-6e. What methodology is used to determine margin requirements?

The margin requirement can be arbitrarily determined by forex providers as long as it doesn't fall below 4% of the size of the actual transaction. Even if the level of the exchange rate is the same, the required margin may vary depending on the Forex firm.

Some Forex businesses use the exchange rate at the time to establish the required margin amount in real time, while other Forex companies use the exchange rate at the end of the previous business day to determine the required margin amount the following day. Additionally, some Forex brokers apply a predetermined margin amount for a set time period, such one week, unless there is a very substantial movement in the exchange rate.

Additionally, there are Forex businesses that establish a minimal margin requirement for currency pairings with relatively low exchange rate levels, and there are Forex companies that set a ratio of more than 4% for currency pairs with quite high price movements.

You should check the website of the Forex business you plan to trade with in advance to see how the needed margin amount is determined and how much you can deal with.