Tariff classification rules determine excise headings and duty bases, prioritising specific descriptions and essential character. The Fourth Schedule prescribes interpretative rules for tariff classification-headings and notes control legal classification, with hierarchy: most specific description, material giving essential character, then last heading numerically if equal; residual goods by affinity. It sets out chapterised tariff entries with units and duty bases; Chapter 24 defines tobacco and nicotine product terms and treats certain market preparation acts as manufacture, while Chapter 27 defines petroleum product categories and links tariff items to technical standards and duty expressions, with amendment annotations noting subsequent legislative changes.