The broker fee is due on order creation for all non-immediate orders and is based on a percentage of the total order value. Starting at 5% of the order value, the skill "Broker Relations" reduces the fee by 0.3% per level. In addition, increased standings with the owner of the NPC station where the order is placed may reduce it by up to another 0.2% with maximum standing, and good standings with the owners faction can reduce the fee by further 0.3%, to a minimal broker fee of 3% of the order value. This results in the following formula to calculate the percentage for the broker fee:
The Broker Fees only take unmodified standings into account, so skills that increase your effective standing, such as Connections or Diplomacy, do not have an effect on these fees.
If an order is changed to a different price, the difference in broker fee has to be paid with committing the change. The exact formula how to calculate the broker fee for changing the price of an order can be found within the article "Buy and Sell Orders".
Broker Fees will be paid to the station owner. However, when charging fees for creating/modifying an order on an Upwell structure, only half of the fee will go to the structure owner. The other half will go to an NPC as an ISK sink. The Broker Relations skill does not apply on orders on Upwell structures.
Sales taxes are due after an item has been sold, and are payable by the seller. They will be automatically deducted from the sales transaction and start at 5% of the sales price. This percentage can be reduced down to 2.25% through the "Accounting" skill.