净出口，或称贸易余额，是指一国在一定时间内的出口总值与其进口总值的差额。

实务上，净出口（贸易余额）有时又细分成有形商品和无形服务两个部份。如美国商业部的《Survey of Current Business》报告书中，有着「商品贸易余额」（Merchandise Trade Balance）和「服务贸易余额」（Balance on Services ）的项目；在英国则使用「有形贸易余额」（visible balance）和「无形贸易余额」（invisible balance）的称呼。

The commercial balance or net exports (sometimes symbolized as NX), is the difference between the monetary value of exports and imports of output in an economy over a certain period, measured in the currency of that economy. It is the relationship between a nation's imports and exports. A positive balance is known as a trade surplus if it consists of exporting more than is imported; a negative balance is referred to as a trade deficit or, informally, a trade gap. The balance of trade is sometimes divided into a goods and a services balance.