Question: what is the purpose of vat in south africa
[{'answer': 'Central government revenues', 'provenance': [{'wikipedia_id': '31540091', 'title': 'Taxation in South Africa', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 27, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]