When you hold a forex position overnight, your broker applies a rollover adjustment, commonly called a swap, to your account. This happens because forex trading involves two currencies, and each currency has an interest rate set by its central bank. In simple terms, you are effectively borrowing one currency to buy another, and the difference between their interest rates creates a small daily credit or charge. Rollover is normally applied at a set time each day, often in the late evening, and positions still open at that moment receive the adjustment for holding them into the next trading day.

For short-term traders who close all positions before the end of the day, rollover rarely matters. For swing traders who hold positions for days or weeks, however, swaps accumulate and can noticeably affect results, especially on larger positions. Beginners are often surprised by a small debit or credit appearing overnight with no trade closed, and they mistake it for an error or a fee. Understanding rollover in advance removes that surprise and lets you factor overnight costs into your plan, just as you factor in spreads when you enter a trade.

Swap rates differ because interest rate differences differ. If you buy a currency with a higher interest rate using a currency with a lower interest rate, you may earn a small positive swap; if you do the reverse, you may pay a negative swap. For example, buying a higher-yielding currency against a lower-yielding one tends to earn rollover, while selling that same pair tends to cost rollover, although the exact amounts also include your broker's markup and market conditions. This is why the same pair can have a positive swap in one direction and a negative swap in the other, and why swaps change over time as central banks adjust rates.

Your broker's trading platform normally shows the long and short swap values for each pair in the contract specifications, usually expressed in points per lot per day. Check these values before holding a trade overnight, and compare them across pairs if you trade several currencies. Some pairs, particularly those involving higher-yielding emerging market currencies, can carry much larger swaps than major pairs like EUR/USD. A strategy that looks profitable on price movement alone can become far less attractive once weeks of negative rollover are added, so always consider swaps as part of the total cost of holding a position.

One quirk that catches beginners out is the triple swap day, usually on Wednesday. Because forex trades settle two business days later, holding a position over the weekend means covering extra days of interest, and brokers apply this by charging or crediting three days of rollover on one weekday, most commonly Wednesday. This means a position held through Wednesday's rollover time can receive three times the normal daily swap, whether positive or negative. If you open a trade on Wednesday afternoon and close it on Thursday morning, you may still have paid or earned the triple amount, depending on your broker's exact timing.

The practical lesson is simple: check your broker's rollover schedule and avoid surprises by planning around it. If your swap is negative and large, you may prefer to close before Wednesday's rollover or reduce size, while a positive swap trader may deliberately hold through it — but only if the trade itself still makes sense on price grounds. Never hold a weak trade solely to collect a swap, because a normal price move can easily wipe out many days of rollover income. Use the calendar of rollover times as part of your routine, alongside the economic calendar, when you manage open positions.

Start by finding the swap values in your platform before you trade a new pair, and note whether the long and short swaps are positive, negative, or close to zero. For day traders, swaps will rarely change decisions, but for swing traders, add an estimate of total rollover to your profit target: if you expect to hold for ten days and the daily swap is negative, your price target needs to cover that cost plus the spread to break even. Some traders avoid pairs with very negative swaps for long holds altogether, choosing alternatives with smaller carrying costs, while others specialise in positive carry trades — but that approach still carries full price risk and requires careful risk management.

Finally, remember that swaps are not fixed forever. Central bank rate changes, broker policy updates, and market liquidity can all move swap rates, so recheck them periodically rather than assuming last month's values still apply. Keep a note of rollover costs in your trading journal, especially for longer trades, so you can see their true impact on your results. Rollover is a normal, transparent part of forex trading, not a hidden trap, and traders who understand it can plan around it calmly instead of reacting with surprise when it appears on their statement.