What are maker and taker orders? What does “Post only” do?
Market makers are people who place new orders on the order book, adding liquidity to the market. Takers are people who place trades that match with these existing orders, taking liquidity out of the market.
Nash charges no fees for maker orders. When placing a limit order, you can check the box “Post only” so that your order is only ever a maker. This will allow you to avoid fees.
If you choose the option “Post only”, your order will only ever be a maker. It will never match with any orders already on the book and will wait for a taker to match with it. If any part of the order would execute immediately (e.g. if you wish to buy for a price above current market price), the entire order will be rejected.