Some bonuses may stipulate a turnover requirement. This is the amount that has to be bet using funds in the bonus wallet before any winnings generated from the bonus become withdrawable. All bonus winnings are kept in the bonus wallet until the turnover requirements are complete.
To opt into paying just 2% commission, simply visit the 'My Account' section of your Betfair account and select the 'Basic' rewards plan. The 2% commission rate will be applied to your account immediately and you can start making those commission savings.