The UN tax committee, which has a new panel of committee members, is holding its 15th session in Geneva this week.
Peters and Mensah, who were also part of the previous UN tax committee, will hold their new positions for two years.
Peters is the policy manager at the Inland Revenue in New Zealand and is based in Wellington. Her main focus is international tax.
Mensah, based in Accra, is assistant commissioner in charge of legal affairs and international taxation agreements at the Ghana Revenue Authority. He specialises in international treaties and is the lead treaty negotiator for the Ghana double taxation treaty team. He also drafts tax legislation, and is the coordinator of the subcommittee on extractive industries taxation for developing countries.