BPX employs the maker-taker model with the purpose of maximizing liquidity and encouraging 'market makers'.

In a maker-taker model the 'taker' is a trader who removes the liquidity from the book by placing an order that matches immediately with an existing order on the book. Taker pays the fee from the committed trade.

The 'maker' is a trader who provides liquidity to the order book by placing a limit order below the best ask price for buy and above the best bid price for sell.