【1】tax： 普通用词，指政府以各种不同方法向个人或单位征收所得税、房地产税等各种税款。侧重实际征收金钱。

No-one enjoys paying tax. 没人喜欢纳税。

They are calling for large spending cuts and tax increases. 他们呼吁大幅度削减开支并提高税收。

a cut in tax on new cars. 降低新车所缴纳的税款。

a pledge not to raise taxes on people below a certain income. 对收入低于一定水平的人不提高税收的承诺。

His decision to return to a form of property tax is the right one. 他决定恢复征收财产税是正确的。

She was fined for tax evasion. 她因逃税而被罚款。

Her accountant was good at exploiting tax loopholes. 她的会计善于利用税收漏洞。

【2】关税：主要是指政府对进口大批商品所征收的的关税

英文解释：A tariff is a tax that a government collects on goods coming into a country.

America wants to eliminate tariffs on items such as electronics. 美国打算取消电子产品等的关税。

The government decided to impose a protective tariff on foreign cars. 政府决定对进口汽车征收保护税。

There is a very high tariff on jewelry.   宝石类的税率很高。

He was anxious on the tariff question.   他对关税问题感到担心。

High tariffs often cause a diversion of trade from one country to another.   高额关税常使贸易从一国转往另一国。

【3】duty 主要是指向购买的特殊商品向政府部分支付的税/关税.

英文解释：Duties are taxes which you pay to the government on goods that you buy. 

They are pressing the Chancellor to reduce excise duty on beer. 他们正给总理施压，要求降低啤酒的消费税。

Import duties still average 30%. 进口税的平均水平仍然在 30%。

customs duties 关税

You pay the duty at the desk and get the receipt. 你可以在出纳台交税，然后拿到收据。

The government imposes a special duty on oil. 政府征特殊石油税。

The duty on imported vodka has been raised. 进口伏特加的关税已经提高了。

New duties will be imposed on wines and spirits.   酒类要征收新税。

This article is free of duties.   这货物免税。

The article is subject to customs duties.  这商品需纳关税。

Our nation levied duties at certain fixed rates upon wine.   国家根据固定税率对酒征了税。