Your fee tier is based upon total USD trading volume over the trailing 30-day period. Transactions made on books quoted in USD , e.g. BTC-USD, are counted as the total USD amount of each filled order. Transactions made on non-USD books are converted to USD based on the most recent fill price on the respective book. For example, the USD volume of a purchase of 1 ETH on the ETH-BTC book, will be immediately converted based on the most recent fill price on the ETH-USD book.
When you place an order at the market price that gets filled immediately, you are considered a taker and will pay a fee of 0.25%.
When you place an order, which is not immediately matched by an existing order, that order is placed on the order book. If another customer places an order that matches yours, you are considered the maker and will pay a fee between 0.35%.
When you place an order that gets partially matched immediately, you pay a taker fee for that portion.
The remainder of the order is placed on the order book and, when matched, is considered a maker order.