Direct answer
Rollover for USD/PLN is the financing effect applied when a position is held overnight. In general terms, it comes from the interest-rate difference between USD and PLN, converted into a percentage of the position’s notional value and then adjusted by the provider’s rollover convention. Many providers also apply a special “triple” treatment around certain days so that the charge reflects multiple calendar days.
If you want to explain it accurately, it helps to separate three layers: (1) the underlying interest-rate mechanics, (2) the provider’s conversion and adjustment rules, and (3) the calendar convention that may multiply the result.
Mechanism: what rollover is
In spot FX, when you hold a trade beyond the usual settlement window, the position is effectively carried. Rollover is the compensation (or cost) for that carry. Conceptually, it is based on the difference between the relevant short-term interest rates in USD and PLN.
A simple educational model is:
- Choose the interest-rate inputs for each currency (the “short-term” reference rates used for the provider’s calculations).
- Compute an interest differential over the number of days being charged.
- Convert that differential into a financing amount proportional to your position size and the trade direction (long one currency / short the other).
- Apply the provider’s convention for conversion into account currency and how they handle bid/ask and spreads.
“Provider adjustments” matter because the rollover you see is rarely a pure central-bank-rate difference. Providers commonly use internal implementations, such as their own financing curves, their own mapping from reference rates, or markups/discounts embedded in the rollover figure.
Mechanics: interest inputs and direction
A USD/PLN trade links two legs:
- One leg earns interest at USD’s reference rate (if you are effectively long USD).
- The other leg costs interest at PLN’s reference rate (if you are effectively short PLN), or vice versa.
So the rollover sign depends on trade direction. If the interest on the “long” side is higher than the interest on the “short” side, rollover tends to be credited; if it is lower, it tends to be charged. This is a general direction rule, not a guarantee for any specific provider’s displayed number.
For an educational example, assume:
- A notional position size (the amount that the provider uses as the basis for financing),
- A USD reference rate and a PLN reference rate,
- A day-count basis (how providers translate annual rates into daily rates),
- And a carry period (1 day, or 3 days in a triple-swap convention).
Then the financing amount is proportional to: (rate differential) × (days) × (notional basis) with conversion steps to express it in the account’s currency. Different providers may use different day-count methods or different notional bases, which changes the final displayed rollover.
Mechanics: provider adjustments and “triple-swap” conventions
Provider adjustments
Even with the same underlying idea—interest differential—providers can produce different rollover outputs because they may:
- Use different reference-rate proxies or internal rate curves;
- Apply adjustments to reflect their own hedging or pricing assumptions;
- Convert between currencies and quote formats using provider-specific rules;
- Implement rollover using bid/ask or margin-related conventions.
So, for independent verification, you generally need the provider’s own rollover methodology (often described in account or contract documentation). Without that documentation, you can only explain the concept, not reproduce an exact provider-specific number.
Triple-swap (calendar effect)
A “triple-swap” convention means the financing charge/credit is multiplied so it covers more than one calendar day. The need arises because some markets do not settle on weekends in the same way as weekdays, so the carry effect for holding through a specific rollover window represents a longer holiday period.
In practice, providers decide on which rollover window the extra day(s) apply. The key point for explanation is not the exact timing for one provider, but the general mechanism: rollover is normally computed for 1 day, and under certain calendar conditions it is computed for 3 days (or another multiple), producing a larger financing effect.
Limitations and failure modes (what can make rollover differ)
- Provider-specific methodology: The displayed rollover may not equal a simple central-rate differential. Day-count conventions, conversion rules, and internal adjustments can change the result.