When you use a Multiplier, you increase the total size of your trade. 

Say, you invest £120 with a Multiplier of 5 in Stocks. The total Trade Size is £600, meaning that we have to reserve an additional £480 for this position. We don't charge you for this unless you keep this position overnight. In that case, you need to pay a small fee for the £480 that you 'borrow' from us.  If you should decide though to close the position the same day, this additional fee will not be applicable.

The additional fee that we charged, we call it 'Financing Fee'.  It is an interest rate on the additional amount that we need to reserve, to make sure that you can use the Multiplier.  

For more detailed information regarding this, please check the FAQ article dedicated to the "Financing Fee" (What do I pay for the Financing Fee?)

If you have any further questions in regards to this, please feel free to contact us via email at BUX Support.