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.
Betfair has a standard commission rate of 5%. That applies to almost every sport, in every country, around the globe & except Australia. Due to the differing fees charged by the NRL and the various racing commissions, Betfairs commission rate in Australia is variable.