Common compounds: 交税 (pay tax), 免税 (tax-free), 关税 (customs duty), 所得税 (income tax), 增值税 (VAT). The verb for paying tax is 交 (jiāo) or 缴 (jiǎo), not 付 (fù).
history
禾 (grain) + 兑 (exchange) - in ancient times, taxes were paid in grain.
The grain radical signals that 税 belongs to agriculture/economics - historical taxes in imperial China were paid in harvested grain. Same radical drives 租 rent, 秋 autumn-harvest, 私 private (-grain), and 科 category.
Provides the sound (shuì close to duì family - same series as 说 shuō, 脱 tuō, 锐 ruì). Semantically apt too: 兑 means 'to convert/exchange', which fits taxation as a forced exchange of grain for state services.
