Several parts combine into one character.

税 is a phonetic-semantic compound: 禾 (the "grain" radical, depicting a stalk of millet or rice with a drooping head) + 兌 (duì, "to exchange" — providing the sound). The composite is historically precise: in pre-monetary China, taxes were paid in grain, with farmers handing over a portion of their rice and millet harvest to the state. The character preserves an entire era of agrarian taxation when the harvest itself was the levy. All three CJK regions use the same form 税.

Korean reading "se." 稅金 (segeum, tax — top-frequency Korean noun in news and finance), 所得稅 (sodeukse, income tax), 稅務署 (semuso, tax office — Korea's 국세청 National Tax Service is the agency, but local 세무서 is the citizen-facing office), 課稅 (gwase, taxation / to levy tax), 免稅 (myeonse, duty-free), 消費稅 (sobise, consumption tax / VAT). Korean political vocabulary leans heavily on 稅 in budget debates and tax-reform discussions.

Mandarin shuì, 4th tone. 税 (shuì), 税收 (shuìshōu, tax revenue), 所得税 (suǒdéshuì, income tax), 免税 (miǎnshuì, tax-free), 税率 (shuìlǜ, tax rate). 增值税 (zēngzhíshuì, value-added tax) and 个人所得税 (gèrén suǒdéshuì, personal income tax) are basic Mandarin financial vocabulary.

Japanese on-reading ゼイ (zei) — 税金 (zeikin, tax — everyday word), 所得税 (shotokuzei, income tax), 消費税 (shōhizei, consumption tax — major Japanese political topic; raised from 8% to 10% in 2019, generating major economic and political debate), 税務署 (zeimusho, local tax office — every Japanese citizen interacts with this for annual filings), 免税店 (menzeiten, duty-free shop — keyword for tourist shopping in Japan; major brands like 関西国際空港免税店 anchor airport retail).

Memory aid: rice grain (禾) being exchanged (兌) — handing over a portion of harvest to the state = tax.