Here's what catches most traders off guard: you open a EUR/USD position on Monday morning, hold it through Tuesday night, and discover a $6.50 charge labeled "swap" in your account history. No one closed your trade. The price barely moved overnight. Yet your broker extracted a fee you didn't see coming.
That's a swap rate—the daily interest adjustment applied to positions kept open beyond the market's 5 PM Eastern rollover cutoff. Central banks assign interest rates to their currencies. Trading a pair means you're simultaneously going long one currency (earning its rate) and short another (paying its rate). The gap between these rates creates your swap charge or credit.
A single night's fee looks insignificant. Three dollars here, five dollars there—pocket change on a standard lot position. But swing traders holding for two weeks? That pocket change becomes $70 in accumulated costs, sometimes more than the spread you paid entering the trade. On the flip side, choose the right currency pair and direction, and those daily credits stack up as passive income while you sleep.
Brokers pull these rates from the interbank tom-next market, layer on their markup (usually 1-2% annually), and apply the result automatically at rollover. Since you're trading on leverage, the calculation uses your full position size. Control $100,000 in EUR/USD with just $5,000 margin, and swap gets computed on that entire $100,000—not your margin deposit. This amplifies both costs and credits depending on whi...