Police have charged a 20-year-old man and a 16-year-old school girl in Sydney with raising money for the Islamic State group.

New South Wales Deputy Police Commissioner Catherine Burn said the pair were arrested in the western suburb of Guildford on Tuesday.

She says they will appear in a Sydney court on Tuesday charged with financing terrorism, an offense which carries a potential maximum 25 year prison sentence.

Australian Federal Police Deputy Commissioner Michael Phelan said 14 people had now been charged under the Operation Appleby counterterrorism investigation since 2014.