Direct answer: what “rollover” means for EUR-based positions
Rollover (often called swap) is the net interest effect of keeping a forex position open past the broker’s daily rollover cutoff. If you hold a position from one value date to the next, the provider adjusts your account by an amount intended to reflect the interest-rate differential between the two currencies in the pair, plus provider-specific pricing adjustments. For “EUR Reaction,” treat it as an EUR-referenced instrument whose rollover follows the same general logic: identify the two currencies embedded in the contract, determine whether the position is long or short, then compute or read the overnight interest debit/credit the provider applies.
Mechanism or definition: the moving parts in a rollover calculation
1) Interest-rate differential (the economic core)
The theoretical rollover is driven by the difference between the relevant interest rates of the two currencies. A long position benefits from the currency with the higher notional interest rate (and is charged when reversed), while a short position does the opposite. In practice, “relevant rates” are often approximated from money-market or policy-rate benchmarks, but the exact benchmark is a provider assumption.
2) Conversion to a per-day amount
Even with a differential, you still need a consistent way to scale interest to the holding period. Common inputs are:
- Contract size / notional: the amount the interest is calculated on.
- Day-count convention: how the provider turns annualized rates into an effective daily rate.
- Rollover calendar: the number of days covered by a particular rollover event (usually one day, sometimes more).
3) Broker/provider adjustments
Providers typically do not post the purely theoretical interest differential. Swap values shown on trading platforms can include adjustments such as:
- execution and pricing model assumptions,
- operational costs,
- markups/markdowns in the swap figure,
- internal spread/financing conventions. Because of this, your actual rollover may differ from a simple “rate differential × days × notional” calculation.
4) Triple-swap convention (weekend or non-business-day effect)
Many forex rollovers are configured so that if the rollover crosses non-trading days, the provider applies an amount that reflects multiple days of interest (commonly described as triple-swap). This is not a different formula conceptually; it is the same overnight interest logic scaled to cover a longer effective period.
Worked example (assumptions, not live numbers)
Assume (for illustration only) you have:
- notional amount N (in the quote-currency terms your platform uses),
- annual interest-rate differential Δr between EUR and the other embedded currency,
- day-count factor D that converts annual rates into an effective daily rate,
- a long position orientation that earns interest when EUR is “receiving” under the provider convention. Then the theoretical single-day interest component would look like: interest ≈ N × (Δr × D). If a triple-swap applies, multiply by 3 (or by the provider’s stated “days covered” value) instead of by 1. Your platform’s displayed swap for the order is the authoritative provider-adjusted outcome, which may not match the simplified theoretical computation.
Evidence or example: how to compute or verify what your platform applies
You can verify rollover mechanics independently by using the platform’s own swap/commission line items:
- Record the rollover charge/credit shown for a position that you hold across the rollover cutoff.
- Confirm direction (long vs short) and the contract specification (the two currencies embedded in the instrument).
- Estimate the expected sign (credit vs debit) from the implied rate differential logic.
- Check day coverage: identify whether the rollover event you crossed corresponds to a longer period (often described as triple-swap around weekends).
- Compare difference: if your simplified theoretical estimate does not match, the gap is evidence that provider adjustments or specific benchmark conventions are in play.
A key point: verification is about confirming sign, relative magnitude across days, and whether the provider applies multi-day rollover—not about assuming theoretical equality.
Limitations and risks: what can make rollover differ or fail
- Provider assumptions vary: the benchmark rates, day-count convention, and financing model may differ from what a reader expects. - Swap depends on the contract terms: contract size, leverage-like presentation, and currency conversions affect the posted amount. - Spread and costs are separate: rollover is not the only cost/benefit of holding; other items (fees, bid/ask effects) can dominate.