What is a swap in forex?

A swap, also known as rollover interest, is the interest a forex broker charges or pays a trader for holding a position open past the daily market close (usually 5 PM New York time), calculated from the interest rate differential between the two currencies in the pair, plus the broker's own markup.

Why does holding a position overnight cost (or pay) interest?

When you hold a forex position overnight, you are essentially borrowing one currency to buy another. The swap is the interest rate adjustment applied to your trading account for this overnight holding. It starts from the difference in interest rates between the two currencies in the pair you are trading — but the differential is the starting point, not the final figure. Brokers add a markup to both sides, which is why a negative swap is usually worse than the raw differential implies and a positive one smaller. Two brokers can quote different swaps on the same pair on the same night, so the number that matters is the one in your own platform.

If you buy a currency with a higher interest rate and sell one with a lower interest rate, you might earn a positive swap. Conversely, if you buy a currency with a lower interest rate and sell one with a higher interest rate, you will likely pay a negative swap. This charge or payment occurs daily at a specific rollover time, typically 5 PM Eastern Time (New York time).

How can ignoring swaps turn a winning idea into a losing trade?

Many beginner traders overlook swap charges, especially when planning longer-term trades. This oversight is a common mistake that can significantly erode potential profits or even turn a profitable price movement into a net loss. Imagine you anticipate a currency pair to rise over several weeks.

While the market moves in your favor, accumulating negative swap charges daily can eat into your gains. For example, if your trade generates $100 in price profit over a month but incurs $150 in total negative swap fees, your "winning" trade actually results in a $50 loss. This is particularly relevant for swing or position traders who hold trades for extended periods.

Can you see a concrete example of a swap's impact?

Let's illustrate with an example using purely illustrative numbers. Suppose you have a $10,000 trading account and you open a buy position of 1 standard lot (100,000 units) on a currency pair like EUR/AUD. This pair typically carries a negative swap if you are buying it, due to Australia's often higher interest rates compared to the Eurozone.

Assume your broker charges a daily negative swap of -$8 for this position. If you hold this trade for 20 trading days (approximately one month), the arithmetic is not simply 20 × -$8. Spot FX settles two business days forward, so the Wednesday rollover carries three days' swap to cover the weekend — four triple Wednesdays in a month push the real cost closer to -$224 than to -$160. Take -$160 as the floor, not the bill. Now, imagine your trade moved in your favor, and you made a gross profit of $120 from price appreciation. After factoring in the swap, your net result is $120 (price profit) − $224 (swap over four weeks, triple Wednesdays included) = −$104. Even at the naive −$160 the trade was already a loss; the real bill is deeper. Despite the price moving as you expected, the negative swap turned your winning idea into a losing trade.

How can positive swaps be factored into a trading strategy?

Not all swaps are negative; you can also receive positive swap payments. This typically happens in a "carry trade" strategy where a trader buys a currency with a relatively higher interest rate and simultaneously sells a currency with a lower interest rate. If held long enough, accumulated positive swap can add up even when the price barely moves. It is also how the carry trade works — and the reason it is dangerous: the position earns slowly and unwinds fast, so a single volatile week can erase months of accrual. The swap is never the reason to take a trade; it is a cost or a rebate on a trade you already wanted.

Before entering such a trade, it's crucial to understand the interest rate differentials and associated swap rates. ForexCommand's CTS (Carry Trade Score) can help identify pairs with significant positive swap potential, while the MRS (Market Readiness Score) can provide insights into overall market conditions that might favor or disfavor longer-term carry strategies. Always check your broker's specific swap rates, as they can vary.