Every open forex position settles eventually, and most retail platforms never actually deliver currency into your bank account. What happens instead is a nightly accounting event called rollover, and its price is the swap rate. Many traders ignore it for months, then discover it has quietly eaten hundreds of dollars from a position they believed was profitable. This article explains what rollover is, where the charge comes from, who pays and who receives it, and how to check the numbers before you hold a position overnight.

What rollover actually is

Foreign exchange trades in the interbank market settle on the spot value date, normally two business days after the trade (T+2). A trade made on Monday settles on Wednesday. But a retail trader does not want to take delivery of euros and dollars every time they open a position; they want to keep trading until they choose to close. [1]

So at the end of each trading day, the broker rolls every open position forward to the next business day. A position with a Wednesday value date becomes Thursday; a position with a Friday value date skips the weekend and becomes Monday. [1] In practice this happens on Wednesday evening for most brokers, which is why weekend interest lands on one specific night rather than being spread across Saturday and Sunday.

Because the position keeps being pushed to a later settlement date, the roll has a price. In wholesale markets, rolling a position means executing a foreign exchange swap: a simultaneous purchase and sale of the same currency amount at two different dates, typically spot to forward. [2] The retail equivalent is a nightly credit or debit on your account, known as the swap fee or rollover fee.

Where the charge comes from

The swap rate is not an arbitrary broker fee. It is anchored to the interest rate differential between the two currencies in the pair. [1]

In the wholesale market, the forward rate is tied to spot by interest rate parity: the forward rate moves away from spot roughly in proportion to the difference between the interest rates of the two currencies multiplied by the time to settlement. The gap between forward and spot is quoted in forward points, or swap points, and those points are roughly proportional to the interest rate differential. [2] When your broker rolls your position, it is effectively transacting around that forward curve, and passes the resulting amount through to your account as the nightly swap.

That also explains why swap rates change. When central banks raise or cut policy rates, the differential between the currencies shifts, and every broker's published swap rates for the affected pairs move with it. A swap that cost half a pip per night in one year can cost two pips the next, purely because interest rates moved.

Who pays and who receives

The direction of the payment depends on which side of the pair you are on. [1]

If the interest rate on the currency you are long is higher than the rate on the currency you are short, you receive the interest: this is positive carry. If the rate on your short currency is higher than the rate on your long currency, you pay: negative carry. Borrowing low-yielding currency to hold high-yielding currency is the classic carry trade, and the nightly swap credit is the retail mirror of that trade. [3]

Two features of this system are worth internalizing:

• The swap can be negative in both directions. Brokers commonly apply an admin markup on top of the interbank swap, so sometimes going long or short of the same pair both cost money overnight. This is a real cost of doing business, similar to the spread, not an error.

• Positive carry is not free money. A swap credit of a fraction of a pip per night is tiny compared with typical exchange-rate movement. Carry trades earn small, steady amounts in calm markets and can lose large amounts when the exchange rate moves against them; the yen carry trade's collapse in 2008 is the standard example. [3]

A worked example (illustrative)

The numbers below are a pure illustration of the arithmetic, not any actual broker's current rates. Real swap rates differ per broker and change with interest rates.

Suppose you hold a long position of 10,000 units of a currency pair (a 0.10 mini lot where one pip is worth about 1 unit of the quote currency). Suppose the interest rate on the currency you are long is 3.00% and the rate on the currency you are short is 4.25%. The differential is 1.25 percentage points against you.

• Annual cost on the position: 10,000 × 0.0125 = 125 in quote currency per year.

• Per night: 125 ÷ 365 ≈ 0.34, or about a third of a pip per night.

• On the triple-swap night (typically Wednesday): three nights' worth, about 1.03.

• Held for a month: roughly 10.27, about 10 pips — before spread, commission, or any price movement.

The same position flipped the other way would earn about the same amount per night before broker markup. The point is proportionality: at these rate levels the swap is meaningful for positions held weeks, negligible for a one-night scalp, and the weekend triple charge is the single largest nightly event of the week.

How to check your swap exposure

• Look up the actual rates before holding. Brokers publish swap rates for long and short on each instrument, on their website or in the platform's instrument specification. If you cannot find a pair's swap rates, treat that as a reason to ask before trading it. [1]

• Remember Wednesday is three nights. Most brokers apply the multiplied rollover mid-week; some instruments (for example metals or crypto CFDs, which settle T+1 or T+0) charge on different nights. Check the instrument's own schedule.

• Re-check after big rate moves. Because swap rates track interest rate differentials, they are not constants. Central bank decisions move them.

• Know the swap-free option and its trade-off. Accounts that waive swap charges exist (often marketed to traders who avoid overnight interest for religious reasons), but they usually replace the swap with a fixed administrative fee after a set number of days. The swap does not disappear from economics; it is restructured. [1]

The bottom line

Rollover is the nightly price of keeping a leveraged position open past settlement. It is driven by the interest rate differential between the two currencies, applied per night, and tripled on the night that covers the weekend. For short holds it is background noise; for multi-week positions it is a real line item that belongs in your trade plan next to the spread and commission. Checking the long and short swap rates on your broker's instrument page takes seconds and prevents the most common surprise: a position that was right about direction and still lost money to the calendar.

Sources

1. Wikipedia, "Rollover (foreign exchange)" — https://en.wikipedia.org/wiki/Rollover_(foreign_exchange)

2. Wikipedia, "Foreign exchange swap" — https://en.wikipedia.org/wiki/Foreign_exchange_swap

3. Wikipedia, "Carry (investment) / Currency carry trade" — https://en.wikipedia.org/wiki/Currency_carry_trade