You pay gas any time you send a transaction to the Ethereum blockchain. There are several instances including:
- Wrapping ETH
- Unwrapping ETH
- Enabling a token allowance
- Filling an existing order ("taker")
- Cancelling an order
- Sending tokens or ETH from your wallet
Why Don't I Pay Gas to Create an Order?
When you create an order, you're signing your willingness to execute a trade with specific parameters (quantity, price, expiration). The order is hosted off-chain by us, so nothing is settled on the blockchain until an order is executed.