Direct answer
Rollover in forex is the value adjustment applied to an open position when the trading day rolls over into the next settlement/valuation cycle. It is often described as an “overnight swap,” and it can be a cost or a credit depending on the position’s direction (buy vs sell) and the instrument’s terms. The practical point is simple: if you hold a forex position across the rollover time, the position’s value is typically adjusted to reflect the product’s overnight financing component.
Mechanism and basic model
A straightforward way to think about rollover is to separate two ideas:
- Holding overnight: whether your position remains open past the rollover time.
- Rollover adjustment: the contract-driven monetary change that follows from that overnight holding.
In most forex market practice, the rollover adjustment is linked to interest-rate differentials implied by the currencies in the pair, combined with provider-specific contract terms (such as how the swap is calculated and any additional components embedded in the quote). Because providers may use different formulas and conventions, the same “pair” name can still produce different rollover outcomes across different venues.
A concrete, assumed example (no live rates)
Assume you hold a position from just before to just after the daily rollover timestamp. Suppose the contract terms specify that, for your trade direction, the overnight swap is a debit of X per day. Under that assumption, the account balance generally decreases by X (or an amount close to it after any scaling factors like position size or contract units) when rollover occurs. If the swap were instead defined as a credit, the same logic would produce an increase.
The key is that the example depends on assumptions about X and the contract’s rollover convention; without those, you cannot accurately quantify the rollover cost.
Adjacent concepts and what rollover is not
Rollover is often confused with other effects of holding trades:
- Not the same as spread: the spread is the transaction cost embedded in the entry/exit prices; rollover is an overnight adjustment tied to contract financing.
- Not the same as commissions: commissions (if any) are separate from swap and typically relate to execution, not overnight financing.
- Not a guaranteed profit engine: a credit from rollover does not ensure an overall gain. Other drivers—price movement, liquidity, and changing contract terms—can outweigh any overnight credit.
Limitations, risks, and failure modes
Rollover has material limitations readers should account for:
- Provider and contract variability: rollover conventions differ by provider and instrument specification. Without the provider’s own contract terms, estimates may be wrong.
- Timing and cut-off rules: rollover can depend on a specific timestamp and the market’s valuation cycle. If your position is opened/closed near that time, outcomes may not match simple “calendar day” assumptions.
- Changing inputs: even if the interest-rate logic is stable in principle, the underlying assumptions can change as markets and provider calculations update.
- Direction sensitivity: rollover can differ for buys versus sells in the same currency pair, so using one number for both directions can lead to systematic misestimation.
Verification and next question
To verify rollover facts independently, readers should check the contract specifications for the instrument and the provider’s swap/overnight financing description, focusing on: the rollover timestamp, whether swap is charged or credited by direction, and how the calculation scales with position size.
A useful next question is: Does your provider publish the swap rate as a predictable table for your specific instrument and trade direction, or only explain the method and apply it dynamically? That difference strongly affects whether you can estimate rollover costs ahead of time.